close all open forms before closing the current one

Question

I have total 4 forms .. when a button on form2 is clicked it loads form3 and minimize form2 and on close of form3 it refocus form2 and same with form4 it loads from a button on form3 and form3 is minimized

  
so if I returned to form2 and clicked the x button it gives an error because form3 wants to refocus form2 that is already closing
please help