Hi Eddie. Ivan presented the perfect code which used API.
So, I proposed the following method as another way.
It is the method of making all letter to "capital letter" compulsorily.
'//Please copy this into a Thisworkbook Module
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Source As Range)
Dim rng As Range
With Application
.EnableEvents = False
For Each rng In Source
rng.Value = UCase(rng.Value)
Next
.EnableEvents = True
End With
End Sub