If you haven't already done so, check the combo box to make sure that it is bound the child (?) field correctly (if you bind your cbos, that is) and that the row source isn't the same as the child or parent table. I know it sounds silly...

The calculations *probably* aren't the problem. But grids are a pain to use for data entry...especially with combo boxes. If they are of any size at all--even 100 records--the grid can be unbearably slow. I eventually moved all my data entry out of the grid, and just use the grid for navigation and display. Everything is much simpler and more stable.

>Yes I do have combo boxes in the grid and even calculations in the grid.