Integer increase/decrease format - %dd
Supplies an spin control button to go with an %rd edit box. %dd takes one
integer argument that specifies the amount the value in the edit box is to be
increased or decreased when the user clicks on the control. The resulting value
is always a multiple of the increase. A call-back function can be supplied with
the corresponding %rd format. %dd may also be used with %rs.
c--- %`rd displays an integer - not user changeable ---