strWs = ActiveSheet.Name

Select Case strWs
Case "Red": ' Do this
Case "Blue": ' Do that
Case "Yellow":' Do the other.
Case Else: ' Do something else.
End Select

HTH
Paul
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Be advised to back up your WorkBook before attempting to make changes.
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I would like to write a macro by depending on the user SELECTED
worksheet to work on something.

Is it possible to detect (know) which page or pages are selected by the
user? please

Thank a lot!!