Put this code in the Thisworkbook code module
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
On Error GoTo wsc_exit
Application.EnableEvents = False
If Target.Column = 2 Then
Select Case Right$(Target.Value, 1)
Case "0": Target.Offset(0, -1).Value = Int(Target.Offset(0, -1).Value)
Case "1": Target.Offset(0, -1).Value = Int(Target.Offset(0, -1).Value) + 1 / 4
Case "2": Target.Offset(0, -1).Value = Int(Target.Offset(0, -1).Value) + 1 / 2
End Select
End If
wsc_exit:
Application.EnableEvents = True
End Sub