Disable master form close button

[Carpy01]

I need to disable the main forms close button when the subform opens. Then enable same button when sub is closed

[weekend00]

when you say subform, do you mean another form which opened by main form?
if yes, you can disable the button when open the subform. in the subform's form_close event, enable the button of main form.

[Carpy01]

Thank you for your reply. I have tried your suggestion however I'm apparently missing something. Would you program your suggestion with vb code or with an expression. You're correct secound form (called subform) opens freom button on main form.
Thanks for your help

[RuralGuy]

If you use the acDialog argument of the OpenForm command, the user cannot get back to the 1st form without closing the 2nd form. It will open the 2nd form as Modal.