Round checkbox in contactform

[masskontroll]

Ok, this one should be real easy: I have a flash contact form that communicates with php. In that form I would like to have an option for the user to state wether he is male or she is female, bij checking either one of two small white circles (marked M or F). Like in the ‘Post Icons’ menu directly under the message when you type a post or reply! Those round checkboxes - how can I add those to a contact form? Thanks!