End Google Ads 201810 - BS.net 01 --> hi everybody,

I use toolstrip button in windows application using c#.
i have toolstrip in mdi child form.
when i click the toolstrip button it open the related form.
The prob is here that i clicked that button again it open another form.
the related form opened again & again when i clicked.
i need only the form is opened once when i click it multiple times.
please help me.