I am a bit confused here. Do you mean combo box, check box or radio button? Typically for yes/no answers, one would use a checkbox. Radio buttons work in groups. If you place several radio buttons on a form, they are part of a group based on the form. Only one will be selectable at a time. Use a GroupBox to organize radio buttons into groups.
Checkboxes are usually used to provide a Yes/No response. They tend to be easier to use and understand than having a series of drop-down combo boxes.
As to your specific question, without the code for the form I can't tell
you why that behavior may be occurring.
This was first published in July 2002