Well first of all, an Excel workbook (template in your case) is not composed
of tabs, it is composed of one or more worksheets, each of which has a tab.
Your question is so vague no one could answer you. You should provide
examples of what you're trying to accomplish.

Tyro

Quite an open-ended request.

Could you be a tad more specific with the details?

Alert before or after?

Data Validation can alert and prevent users from entering incorrect data.

Conditional formatting can alert users after they have entered incorrect data by
highlighting the data if it does not meet the condtion you set.

Either or both would maybe do the trick.

Gord Dibben  MS Excel MVP