Move all rows 1 down but skip row 26 & Public Function IF problem

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    Select Case Target.Address
    Case "$A$15", "$A$48", "$A$49", "$A$50"
          If CStr(Target.Value) = vbNullString then Target.Value = Date
   End Select
End Sub

Although, you may want to put the datestamp in the Double Click event rather then SelectionChange. Selection is vital to working a spreadsheet and changing cell's value when it is selected can be too volatile for my taste.