Create custom close opportunity

Hi,

I have imported Ribbon Bench and able to create button as "Close Opportunity". I just want to know how to link custom web page or Workflow to close opportunity to "Button".

Rule is : When clicked on Close Opportunity button and should ask info to enter and close, this can be do through java script. if yes, please let me know how to write code.

Can you please share steps to do it ?

Regards

Faisal