Round-shaped buttons.

[bkna besta cc]

Hi all,
I want to put round-type buttons (circular shape) .
I looked out several books but all of them described only rectangle-typed ones.
Even I searched the mailing list but I could not find any solutions.
In there, some people had the same questions but there were no answer...
Really is it impossible?
If possible, please post a simple example.

Best regards,
bkna