Not allow certain cell entries

[Guest]

I have a worksheet setup with 5 tabs. On 3 of the tabs I do not want to be
able to type "123" into any of the cells. Can I write a pop-up or function
for these three tabs within the worksheet?

 

[Bernard Liengme]

You have a WORKBOOK with five WORKSHEETS
Each worksheet has a tab for opening it.
If you group the three worksheets together (Help will tell how), then what
you type in a cell in one will also be entered into the corresponding cells
in the other worksheets.
best wishes