Sub ChangeCase()
Dim tskTask As Task
Dim UpperOrLower As String

Start:
UpperOrLower = InputBox(Prompt:="Enter 'Upper' or 'Lower'", _
Title:="Conver to Upper or Lower Case?")
If UpperOrLower <> "Upper" And UpperOrLower <> "Lower" Then
    MsgBox Prompt:="You did not enter Upper or Lower. Check your spelling", _
    Title:="Error"
    GoTo Start
End If

Select Case UpperOrLower
    Case "Lower"
        For Each tskTask In ActiveProject.Tasks
            tskTask.Text1 = LCase(tskTask.Text1)
        Next tskTask

    Case "Upper"
        For Each tskTask In ActiveProject.Tasks
            tskTask.Text1 = UCase(tskTask.Text1)
        Next tskTask
End Select

End Sub