here is what you want:
//**********************************************
string $pa_result[] = polyAverageVertex -i 0
;
window averageVtxWindow;
string $form01 = formLayout
;
string $button01 = button -l "update"
;
string $slider01 = intSlider -min 0 -max 10
;
setParent ..;
formLayout -e
-af $button01 "top" 0
-af $button01 "left" 0
-af $slider01 "top" 0
-ac $slider01 "left" 0 $button01
-af $slider01 "right" 0
$form01;
window -e -h 48 -w 220 averageVtxWindow;
eval ("button -e -c ("updateVtxSlider " + $slider01 + "") " + $button01);
eval ("intSlider -e -s 1 -dc ("averageVtxSliderCommand " + $pa_result[0] + " " + $slider01 + "") " + $slider01);
showWindow averageVtxWindow;
global proc averageVtxSliderCommand(string $attrName, string $sliderName)
{
int $value = intSlider -q -v $sliderName
;
setAttr ($attrName + ".iterations") $value;
}
global proc updateVtxSlider(string $sliderName)
{
string $pa_result[] = polyAverageVertex -i 0
;
intSlider -e -v 0 $sliderName;
eval ("intSlider -e -s 1 -dc ("averageVtxSliderCommand " + $pa_result[0] + " " + $sliderName + "") " + $sliderName);
}
//**********************************************
this slider goes from 0 to 10. The update button resets the slider and uses the current selection for a new polyAverageVertex-command
enjoy