xVSlider  L T W H Title Variable Min Max Current ShowStr
 xHSlider  L T W H Title Variable Min Max Current ShowStr

These two gadgets are Sliders :

xVSlider is a vertical slider and xHSlider a horizontal one.
L T W H Title and Variable have the same meaning as other gadgets.

Min     : The minimum value of the slider
Max     : The maximum Value
Current : The starting Value of the slider
ShowStr : This is a printf style string specifying the format of
          the value to be shown next to the slider :
          You can specify "%3d" or "%5d Widgets" for example.
          The simplest is to specify "%5d" (the Number 5 means
          the maximum length of the number that the slider can show).

The Title will be placed to the left of the gadget unless told 
otherwise by the GadTitle command

Example :  Run Gui   Source