diff --git a/example/uvwt.irp.f b/example/uvwt.irp.f
index f1c7a87..63655a1 100644
--- a/example/uvwt.irp.f
+++ b/example/uvwt.irp.f
@@ -13,6 +13,15 @@ END_PROVIDER
 BEGIN_PROVIDER [ integer, u1 ]
   integer :: fu
   u1 = fu(d1,d2)
+  integer :: n, m
+  n=3
+  do i=1,n
+    print *,  i
+  enddo
+  m=2
+  do i=1,m
+    print *,  i
+  enddo
   PROVIDE u2
 END_PROVIDER
 
diff --git a/src/command_line.py b/src/command_line.py
index da43acb..b01ba7b 100644
--- a/src/command_line.py
+++ b/src/command_line.py
@@ -27,6 +27,7 @@
 
 import getopt, sys
 from version import version
+import re
 
 description = "IRPF90 Fortran preprocessor."
 options = {}
@@ -42,6 +43,7 @@ options['t'] = [ 'touch'        , 'Display which entities are touched', 1 ]
 options['m'] = [ 'memory'       , 'Debug memory info', 0 ]
 options['z'] = [ 'openmp'       , 'Automatic openMP tasks (may not work)', 0 ]
 options['l'] = [ 'align'        , 'Align arrays using compiler directives', 1 ]
+options['s'] = [ 'substitute'   , 'Substitute values for loop max values', 1 ]
 options['r'] = [ 'no_directives', 'Ignore compiler directives !DEC$ and !DIR$', 0 ]
 
 class CommandLine(object):
@@ -61,6 +63,17 @@ class CommandLine(object):
     return self._defined
   defined = property(fget=defined)
 
+  def substituted(self):
+    if '_substituted' not in self.__dict__:
+      self._substituted = {}
+      for o,a in self.opts:
+        if o in [ "-s", '--'+options['s'][0] ]:
+          k, v = a.split(':')
+          v_re = re.compile(r"(^.*[,| ]+)(%s)(\s*$)"%k.strip())
+          self._substituted[k] = [v, v_re]
+    return self._substituted
+  substituted = property(fget=substituted)
+
   def preprocessed(self):
     if '_preprocessed' not in self.__dict__:
       self._preprocessed = []
diff --git a/src/parsed_text.py b/src/parsed_text.py
index 8902fe1..4a68f81 100644
--- a/src/parsed_text.py
+++ b/src/parsed_text.py
@@ -30,7 +30,7 @@ from irpf90_t import *
 from variables import variables
 from preprocessed_text import preprocessed_text
 from subroutines import subroutines
-import regexps
+import regexps, re
 import error
 
 vtuple = map(lambda v: (v, variables[v].same_as, variables[v].regexp), variables.keys())
@@ -505,10 +505,28 @@ def check_opt():
         do_level -= 1
 check_opt()
 
+######################################################################
+def perform_loop_substitutions():
+  main_result = []
+  for filename, text in parsed_text:
+    result = []
+    append = result.append
+    for vars,line in text:
+      if type(line) == Do:
+        for k,v in command_line.substituted.items():
+          reg = v[1]
+          if reg.search(line.text) is not None:
+            line.text = re.sub(reg,r'\1%s\3', line.text)%v[0]
+      append( (vars,line) )
+    main_result.append( (filename, result) )
+  return main_result
+  
+parsed_text = perform_loop_substitutions()
+
 ######################################################################
 if __name__ == '__main__':
  for i in range(len(parsed_text)):
-  if parsed_text[i][0] == 'psi.irp.f':
+# if parsed_text[i][0] == 'psi.irp.f':
    print '!-------- %s -----------'%(parsed_text[i][0])
    for line in parsed_text[i][1]:
      print line[1]
diff --git a/src/version.py b/src/version.py
index 2be6f8b..71115e0 100644
--- a/src/version.py
+++ b/src/version.py
@@ -1 +1 @@
-version = "1.2.2"
+version = "1.2.3"