EXCEL Form

I am trying to develop an Excel form for my colleagues to be able to access from the network. When they open the form, the intention is that they will be able to fill in some details and then send it (as an attachment) to their manager for approval selecting his or her name from the Outlook Global Address List (GAL) by a button on the form. Once the manager has approved the request, he or she will then send the form (as an attachment) to a mailbox, using another utton of the form. I presume some programming will be required. So far I have put a macro that can attach the form into an Outlook message but don’t know how to make it so that the e-mail address is autoinserted into the To box. Secondly, I don’t know how to insert a control that on click will open up the GAL. Can anyone help? Many thanks, Cent.