Add a sales line after creating a part

I was asked to add a button to the sale order form in the sales line section to create an item. I have also been asked to create a line on the sales order after the new part is created using the new item number. I have added the code on the click method of the button to call the menu item. I was hoping that the code would come back to the calling method after the called form closed, but that was not the case. I am sure this has been ask for by someone before, can anyone give me some information about what I need to do to make this happen?