diff --git a/src/bin/test_simple.rs b/src/bin/test_simple.rs
index bb1df9f..c0d9f5b 100644
--- a/src/bin/test_simple.rs
+++ b/src/bin/test_simple.rs
@@ -1,5 +1,5 @@
 use rand::Rng;
-use rustmp::par_for;
+use rustmp::{par_for, critical};
 use std::time;
 
 #[derive(Debug)]
@@ -11,9 +11,11 @@ struct Student {
 
 impl Student {
     pub fn new(age: u8) -> Student {
-    Student { name: "Default".to_string(),
-          age,
-          gpa: age as f32 }
+        Student {
+            name: "Default".to_string(),
+            age,
+            gpa: age as f32,
+        }
     }
 }
 
@@ -21,23 +23,32 @@ fn main() {
     let numbers: Vec<Student> = vec![];
 
     par_for! {
-    for i in 1..32, capturing numbers {
-    //std::thread::sleep(
-    //    time::Duration::from_secs(
-    //    rand::thread_rng().gen_range(1..10)));
-    let mut lock = numbers.write();
-    lock.push(Student::new(i));
-    println!("Thread {} running!", i);
-    } };
-
-    par_for! {
-    for i in 1..32, blocksize 16, capturing numbers {
-    let mut lock = numbers.write();
-    lock.push(Student::new(i));
-    println!("Thread {} running!", i);
-    } };
+        for i in 1..32, blocksize 4, capturing numbers, {
+            //std::thread::sleep(
+            //    time::Duration::from_secs(
+            //    rand::thread_rng().gen_range(1..10)));
+            critical! {
+                // Automatically locks numbers as read+write,
+                // and makes the result accessible as number
+                readwrite numbers;
+                numbers.push(Student::new(i));
+            }
+            println!("Thread {} running!", i);
+        }
+    }
 
     for num in numbers {
-    println!("{:?}", num);
+        println!("{:?}", num);
     }
+
+    //let mut local = 0;
+    //par_for! {
+    //for i in 1..32, blocksize 1, capturing numbers, private local, {
+    //local += 1;
+    //println!("{}", local);
+    //let mut lock = numbers.write();
+    //lock.push(Student::new(i));
+    //println!("Thread {} running!", i);
+    //} }
+
 }
diff --git a/src/lib.rs b/src/lib.rs
index af0e402..5b17c0a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -39,18 +39,54 @@ impl<T> Capture<T> {
     }
 }
 
+#[macro_export]
+macro_rules! critical {
+    (read $($r:ident)+; readwrite $($w:ident)+; $($ops:tt)+) => {
+        {
+            $(let $r = $r.read();)*
+            $(let mut $w = $w.write();)*
+            $($ops)*
+        }
+    };
+    (readwrite $($w:ident)+; read $($r:ident)+; $($ops:tt)+) => {
+        {
+            $(let $r = $r.read();)*
+            $(let mut $w = $w.write();)*
+            $($ops)*
+        }
+    };
+    (readwrite $($w:ident)+; $($ops:tt)+) => {
+        {
+            $(let mut $w = $w.write();)*
+            $($ops)*
+        }
+    };
+    (read $($r:ident)+; $($ops:tt)+) => {
+        {
+            $(let $r = $r.read();)*
+            $($ops)*
+        }
+    };
+}
+
 #[macro_export]
 macro_rules! __internal_par_for {
-    ($name:ident, $iterator:expr, $size:expr, $($captured:ident)*, $blk:block) => {
+    (var_name($name:ident),
+    iterator($iter:expr),
+    blocksize($size:expr),
+    captured($($captured:ident)*),
+    private($($private:ident)*),
+    $blk:block) => {
         let mut __rmp_tasks = Vec::new();
         $(let $captured = rustmp::Capture::new($captured);)*
         {
             let __rmp_tpm_mtx = rustmp::ThreadPoolManager::get_instance_guard();
             let __rmp_tpm = __rmp_tpm_mtx.lock().unwrap();
-            let __rmp_iters = __rmp_tpm.split_iterators($iterator, $size);
+            let __rmp_iters = __rmp_tpm.split_iterators($iter, $size);
             for iter in __rmp_iters {
                 $(let $captured = $captured.clone();)*
                 __rmp_tasks.push(rustmp::as_static_job(move || {
+                    $(let mut $private = $private.clone();)*
                     for &$name in &iter
                         $blk
                 }));
@@ -59,6 +95,54 @@ macro_rules! __internal_par_for {
         }
         $(let $captured = $captured.unwrap();)*
     };
+    // Parse blocksize
+    (var_name($name:ident),
+    iterator($iter:expr),
+    blocksize($size:expr),
+    captured($($captured:ident)*),
+    private($($private:ident)*),
+    blocksize $new_size:expr,
+    $($rem:tt)+) => {
+        rustmp::__internal_par_for!(
+            var_name($name),
+            iterator($iter),
+            blocksize($new_size),
+            captured($($captured)*),
+            private($($private)*),
+            $($rem)*)
+    };
+    // Parse capturing
+    (var_name($name:ident),
+    iterator($iter:expr),
+    blocksize($size:expr),
+    captured($($captured:ident)*),
+    private($($private:ident)*),
+    capturing $($new_captured:ident)*,
+    $($rem:tt)+) => {
+        rustmp::__internal_par_for!(
+            var_name($name),
+            iterator($iter),
+            blocksize($size),
+            captured($($new_captured)*),
+            private($($private)*),
+            $($rem)*)
+    };
+    // Parse private
+    (var_name($name:ident),
+    iterator($iter:expr),
+    blocksize($size:expr),
+    captured($($captured:ident)*),
+    private($($private:ident)*),
+    private $($new_private:ident)*,
+    $($rem:tt)+) => {
+        rustmp::__internal_par_for!(
+            var_name($name),
+            iterator($iter),
+            blocksize($size),
+            captured($($captured)*),
+            private($($new_private)*),
+            $($rem)*)
+    };
 }
 
 /// "parallel for" wrapper
@@ -67,22 +151,13 @@ macro_rules! __internal_par_for {
 /// Current implementation save limited (max depth 32) stack space for macro expansion.
 #[macro_export]
 macro_rules! par_for {
-    (for $name:ident in $iterator:expr, blocksize $size:expr, capturing $($captured:ident)+, $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, $size, $($captured)*, $blk);
-    };
-    (for $name:ident in $iterator:expr, blocksize $size:expr, capturing $($captured:ident)+ $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, $size, $($captured)*, $blk);
-    };
-    (for $name:ident in $iterator:expr, capturing $($captured:ident)+, blocksize $size:expr, $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, $size, $($captured)*, $blk);
-    };
-    (for $name:ident in $iterator:expr, blocksize $size:expr, $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, $size,, $blk);
-    };
-    (for $name:ident in $iterator:expr, capturing $($captured:ident)+, $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, 1, $($captured)*, $blk);
-    };
-    (for $name:ident in $iterator:expr, capturing $($captured:ident)+ $blk:block) => {
-        rustmp::__internal_par_for!($name, $iterator, 1, $($captured)*, $blk);
+    (for $name:ident in $iter:expr, $($rem:tt)+) => {
+        rustmp::__internal_par_for!(
+            var_name($name),
+            iterator($iter),
+            blocksize(1),
+            captured(),
+            private(),
+            $($rem)*)
     }
 }