radio buttons problem (please help !)

Hi, I need some help with a radio button problem. I have a calculator app and four radio buttons on the form for the four known bases (16,8,2,10). The problem appears when I check one of the radio buttons, the other ones are unchecked. That's fine but how do I know which radio button was checked before I checked the second radio button? I've tried the following: private void radionBtnHexa_CheckedChanged(object sender, System.EventArgs e) { if (radioBtnDecimal.Checked == true) { // ... code here ... } // ... coed here ... } Please help me ! I need help because I've tried in several ways and it doesn't work and it's really important to get this thing working. :( Thanx in advance for any help provided ! :) Cheers to all, Adisor