Avoid validation in certain conditions

Question

Dear experts

I have one windows application and i am residing forms and user controls on different conditions in MDI parent form
My problem is that if i click some button on MDI parent form it should not execute validation of child control
Means if i validate textbox not to allow blank on leave event and if it is blank then even if i click MDI parent form button when that textbox is blank and control is in textbox it should get clicked without validating textbox