I have a MainForm - Split form with datasheet on Right. Each time the user changes the width of the datasheet and thereafter Close the form, he/she is prompted to save not only the change of the MainForm - all Suforms has to be saved too-

I want to turn off the promted savings of Subforms

Please see what witten on MSDN:
https://social.msdn.microsoft.com/Forums/office/en-US/9b5b0533-525b-44b0-b657-f2c715fb5040/why-must-all-subforms-be-saved-again-and-again-when-i-just-adjusting-the-split-on-the-mainform?forum=accessdev