Help: GUI in C++

I'm doing a program compiled in Turbo C++ and have included button-like graphics which the user can click on. (working with registers)

if (in.x.bx==1&&...)//button 1
	 {
          do{
            statements here
            ...
            call function1 (returns the value of x)
          while (x==1)
	  }
      if (in.x.bx==1&&...)//button 2
	 {
          call function2
	 }
      if (in.x.bx==1&&..)//exit button
         {exit(1);}

Problem #1: Is there a way to interrupt what button1 is processing when the user clicks on another button?

Problem #2: When the user clicks on button2 then button1 for the second time, the do-while loop doesn't work. (The user needs to keep on clicking button1 to simulate)

Thanks!