Unhide worksheets with message box entry

I have some code, the purpose of which is to unhide a group of worksheets based on the data entry of one or two cells (H11 and H12). I am trying to enforce this by way of a message box entry. The problem I am encountering is that the only place I can find that it works (more or less) is in the Worksheet_Change event, and the problem with this is that every other line of code that causes a change in the worksheet will invoke the message box. I only want it to appear based on a change in range H11. If i try to to put it in the Worksheet_SelectionChange then it crashes (hard - stack overflows and other errors, including simply shutting down). I'd appreciate any advice here, or maybe there's another way to do it... The terms UnhideOpen, UnhideTSC, UnhideRoutine and UnhideDemo refer to the various worksheet groups.

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Try thiis,

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Cheers

Sorry for rush on time limited machine

Thanks for your help. I had to change the line

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to

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in order to get rid of a "Sub or Finction not defined error. However, when I did that and ran the code, It looks like it's going through a huge loop until an error message appears:

Run-time error -2147417848 (80010108)
Method '_Default' of object 'Range' failed

Then Excel shuts down...