There are many possible ways you could do this. I've not used VB6 in a long time, but from what I can think of there could be two easy ways of doing this.
The first involves the actions of the actual option-buttons. First, double click on the "Disable" option - you should get a sub which is executed when it is enabled or clicked. In this, you would place something similar to the following:
Code:
btnStart.Enabled = False
btnStop.Enabled = False
Depending on what you called your controls.
Now for the enable option, you would double click on that and place the opposite:
Code:
btnStart.Enabled = True
btnStop.Enabled = True
The second way involves checking the checked state of the options when you actually click the "start" button, but as I don't have VB6 installed it is quite hard for me to tell you what to do because I'm almost certain anything I write on the spot won't work.