diff --git a/product/ERP5/Document/PaySheetTransaction.py b/product/ERP5/Document/PaySheetTransaction.py
index 4d078a1f3d1e60b738a4f8e6f2c9704b701a0292..66fceeda694c2403f4bed6f2f9c0713c02473eb5 100644
--- a/product/ERP5/Document/PaySheetTransaction.py
+++ b/product/ERP5/Document/PaySheetTransaction.py
@@ -384,9 +384,9 @@ class PaySheetTransaction(Invoice):
                 # if no calculation script found, use a default method :
                 if not quantity:
                   if base_application <= model_slice_max:
-                    quantity = base_application
-                  else: 
-                    quantity = model_slice_max
+                    quantity = base_application-model_slice_min
+                  else:
+                    quantity = model_slice_max-model_slice_min
               else:
                 localized_calculation_script = getattr(self, script_name, 
                                                        None)
@@ -433,10 +433,6 @@ class PaySheetTransaction(Invoice):
                 base_amount_table[column[share]][row[base_participation]] = \
                                                                       new_val
 
-          # decrease the base_application used for this model line 
-          if cell is not None :
-            base_application -= quantity
-
       if cell_list:
         # create the PaySheetLine
         pay_sheet_line = self.createPaySheetLine(