I have a grid on a form with "table1" as RecordSource .
I set a column with a ControlSource like this:

IIF(EMPTY(table2.item_code), ' ', '#')

table2 is related with table1 based on item_code.
When I activate another form (the form with the grid looses focus)
I have a "total" refresh of the column grid with the same value
(' ' or '#' depending on the value of the current grid row)

Any suggestion ?