I have a master-detail form. I have a tabcontrol that containsorder list with a synthesis of order into first page and master+detail of first pageselecteditem on second page (containing both master heading both detail rows) . I added a computed column inorder list. I used the following expression sum(child(relationname).Field) that generate calculatedcolumn total. Seems that all is working fine and total column contains right values. But the form is very slow,there is a bug on deleting of detail rows (even ifthere is a multiple selectiononly the last row is deleted) and bindingSource position doesn't follow user movement. When i remove calculated column all return to work fine. I don't know what's the problem. Every suggest is appreciated. Thanks in advance.