danikuper,
Just an idea....
Declare a Public variable at module level, so it's accessible from all forms. Make it a Boolean type. In the OnCurrent Event of the main form, set it to False. When another form is updated, set the variable to True in the forms AfterUpdate event. When you return to the main form, test to see if it's set to True, and if it is, update the field. When done, set the variable to False.
hth
Gerhard