Changing Values in ThisWorkbook

I have a workbook that immediately opens a userform when opened. I did this simply by adding the form to Workbook_Open(). This seems to be causing problems however now and I need to either remove this event or the form from opening.

My problem however is that I've sent my workbook out to a number of people and I would prefer to simply fix this by sending them an additional file with 1 button in they can click that will fix this. I have to do it like this because many of the people have already started working on the workbook and can't afford to start over on a new corrected file.

So my questions are as follows:

Is it possible to remove the .show command from a workbook and what the coding for this would be?
Is it possible to disable the userform from being shown or removing it?

Definately the simplest option and I'll suggest this to everyone to use.

Is there however still a way that I can stop the form from appearing without having to use the shift key?