MDI Child show and reactivate

I have One MDI parent Form with a Panel and Panel contains tree buttons. 1 form Form1 and 2 for Form2 and 3 from exit. I am opening From1 as MDIChild by pressing button1 using follwoing Code:

 

Form2 frm2 = new From2();

frm2.MDIParent= this;

frm2.Show();

 

My Problem is this that when press button again it opens an another form2. I see two forms of Form2. However I dont want to open an another From if my form is already opens.

 

Anybody can help? Thanks in advance.

 

Mr.SEA