How to diabale a button when more than two checkboxes are selected

Hai all, I am having a jsp page where i had some entries and a checkbox for each entry. Any user has to select one of the checkboxes and click the download button. This is working fine. But if more than one checkbox is selected, the download button should be disabled. I know that it is a bit of javasript stuff but am not getting it right. so please help me in this regard.

Thanks in advance.....

[411 byte] By [autoa] at [2007-10-3 1:17:59]