Or this if you want to change the text in the cells to Uppercase when you press Enter.
this will work only in Column A.
You must place this event in a sheet module
Private Sub Worksheet_Change(ByVal Target As Range)
Dim cell As Range
If Target.Column = 3 Then
For Each cell In Target.Cells
With cell
If Not .HasFormula And Not IsNumeric(.Value) Then
Application.EnableEvents = False
.Value = UCase(.Value)
Application.EnableEvents = True
End If
End With
Next cell
End If
End Sub
See this webpages also
http://www.mvps.org/dmcritchie/excel/proper.htm
Or
http://www.cpearson.com/excel/case.htm
Here is a macro for changing text cells in the selection
Sub Uppercase_macro()
Dim selectie As Range
Dim cel As Range
On Error Resume Next
Set selectie = Range(ActiveCell.Address & "," & Selection.Address) _
.SpecialCells(xlCellTypeConstants, xlTextValues)
If selectie Is Nothing Then Exit Sub
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
For Each cel In selectie
cel.Value = UCase(cel.Value)
Next cel
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub