how to change selected index of main form

Hi all ,

           I am calling a form from main form. and main form is hidden. 

when i want to go back to the main form then i want to use the same selected index of my list box.

so can any one tell me how to update the selected indx of main form.

i am closing seconf=d form as follow.

 case Keys.Escape:
                    MainForm.thisIsReturningFromShootingview = true;
                    MainForm.shootingViewPersonIndex= personListBox.SelectedIndex;
                   
                
                    this.Close();
                    break;

Thank you in advance.