Focusing into a control by navigation from other form in c#

Question

Sir,

 

I need your help to a navigation problem.

 

This is my first step:-

 

 

 

When I click on the ' + ' button, a new form will popup. Here that form:-

 

 

 

I want to return and focus to the  comboBox control containing  ' +'  control immediately after saving the company.

 

How this possible in c#?, please help me.