diff --git a/bin/osv/fields.py b/bin/osv/fields.py
index beab2ea3b7e..5d373a168ea 100644
--- a/bin/osv/fields.py
+++ b/bin/osv/fields.py
@@ -630,11 +630,9 @@ class function(_column):
         if 'relation' in args:
             self._obj = args['relation']
             
-        if 'digits' in args:
-            self.digits = args['digits']
-        else:
-            self.digits = (16,2)    
-                
+        self.digits = args.get('digits', (16,2))
+        self.digits_compute = args.get('digits_compute', None)
+
         self._fnct_inv_arg = fnct_inv_arg
         if not fnct_inv:
             self.readonly = 1
@@ -656,6 +654,13 @@ class function(_column):
             self._symbol_f = float._symbol_f
             self._symbol_set = float._symbol_set
 
+    def digits_change(self, cr):
+        if self.digits_compute:
+            t = self.digits_compute(cr)
+            self._symbol_set=('%s', lambda x: ('%.'+str(t[1])+'f') % (__builtin__.float(x or 0.0),))
+            self.digits = t
+
+
     def search(self, cr, uid, obj, name, args, context=None):
         if not self._fnct_search:
             #CHECKME: should raise an exception
diff --git a/bin/osv/orm.py b/bin/osv/orm.py
index 62529d34795..0165d4e7a4a 100644
--- a/bin/osv/orm.py
+++ b/bin/osv/orm.py
@@ -2296,7 +2296,7 @@ class orm(orm_template):
         self._columns = self._columns.copy()
         for store_field in self._columns:
             f = self._columns[store_field]
-            if isinstance(f, fields.float):
+            if hasattr(f, 'digits_change'):
                 f.digits_change(cr)
             if not isinstance(f, fields.function):
                 continue