here is the final:
Sub MyCalculator()
Dim aChar As Variant, aRng As Range, iTotal As Long
Set aRng = Selection.Range
For Each aChar In aRng.Characters
Select Case AscW(aChar)
Case 1488 To 1497: iTotal = iTotal + AscW(aChar) - 1487
Case 1498: iTotal = iTotal + 20
Case 1499: iTotal = iTotal + 20
Case 1500: iTotal = iTotal + 30
Case 1501: iTotal = iTotal + 40
Case 1502: iTotal = iTotal + 40
Case 1503: iTotal = iTotal + 50
Case 1504: iTotal = iTotal + 50
Case 1505: iTotal = iTotal + 60
Case 1506: iTotal = iTotal + 70
Case 1507: iTotal = iTotal + 80
Case 1508: iTotal = iTotal + 80
Case 1509: iTotal = iTotal + 90
Case 1510: iTotal = iTotal + 90
Case 1511: iTotal = iTotal + 100
Case 1512: iTotal = iTotal + 200
Case 1513: iTotal = iTotal + 300
Case 1514: iTotal = iTotal + 400
Case 45: iTotal = iTotal * -1 'a minus sign
End Select
Next aChar
MsgBox iTotal
End Sub