Sharepoint 2010 post url address parameters to external site

Hi

I urgently need to POST form fields using a link or button in my sharepoint site. The link/button should submit 3 parameters and post them to an external site so that the parameters are not shown in the url of the destination page.

I tried to do this by adding a form to a web part but sharepoint says that a form already exists so I guess that method is no good. 

Please can you advise if there is an easy way to do this?

many thanks,

Steve