Force 'Save As' Through CommandButton

I have created a tool in excel to facilitate different requests from our sales force. A drop down list in the first worksheet lists the request types. Once the type is selected the user clicks a command button that sends the user to the corresponding worksheet specific to the request type.

My problem is that I need to verify that the cells on the specific worksheet have all been completed. I tried to verify when saving in the workbook module, but I don't know how to only check the selected request worksheet.

One thought was to insert save command buttons on each worksheet and only allow saving through those buttons. (So I would need to remove any saving functionality from the file menu/toolbar.) Then I could attach the verification code to that button on each worksheet. Preventing saving until the requested data was entered.

If this methodology will work I need to know how to do the following:

1) remove alternative saving methods

2) Once those methods are removed, how do I code a command button to check that specific cells are not null and then "save as".

3) if cells are null then, stop save and show msgbox.

I am working in Excel 2003.