How to Change Visibility of TextBoxes depending on ComboBox Selection?

[rodsRisk]

I want certain textboxes to become visible depending on the selection that is made in the comboBox but I can't figure it out and couldn't find any information online.

this is what I have:

                         if (this->cbInstr-> Text = "STOCKS")
			 {
				 this->tbStrike->Visible = false;
				 this->tbExp->Visible = false;
	// Type of instrument: Stock=STK,Option=OPT,Future=FUT, etc.
				 ContractInfo->secType = "STK";
			 }
			 else if (this->cbInstr->Text = "OPTIONS")
			 {
				 this->tbStrike->Visible = true;
				 this->tbExp->Visible = true;
				 ContractInfo->secType = "OPT";
			 }
			 else if(this->cbInstr->Text = "FUTURES")
			 {
				 this->tbStrike->Visible = true;
				 this->tbExp->Visible = true;
				  ContractInfo->secType = "FUT";
			 }