The way to make Form indicate once again automatically after sendkeys execution

Hello
I am improving my application now.

To make Form indicate once again automatically after sendkeys execution, I am combining "visible", "activate" and "sleep" variously, but none works.
Aren't there any good ways?

//A part of program
this.Visible = false;
SendKeys.Send(command);

 if (action == "o")
   {//Open Form again
       System.Threading.Thread.Sleep(10000);//wait 10 sec
       this.Visible = true;
       this.Activate();
   }