Hope I can get some help, I have searched and found some questions and
answers on this subject but its not quite what I'm looking for.

I'll try to explain it, I have a spreadsheet with a number of worksheets
which are all hidden, when you open up the spreadsheet the main page you see
has a few control buttons which take you to different worksheets and vice
versa, what I want to happen is when you click on a button that worksheet
opens and a pop up message or box appears on that worksheet, you then read it
and press OK to close it and carry on in that worksheet.

I hope this is easy to follow, any help would be much appreciated.