The Horizontal Progress Bar can be adjusted by clicking on it. When adjusting is finished the onadjustend event fires. If you attach a function to the onadjustend event (as below) you can get the new value by looking at the .value property (eg myProgress.value).
<script>
window.onload = function (e)
{
var hprogress = new OfficeExcel.HProgress('myc', 83, 100, 0);
hprogress.Set('chart.color', 'green');
hprogress.Set('chart.adjustable', true);
hprogress.Set('chart.margin', 5);
hprogress.Set('chart.tickmarks.inner', true);
hprogress.Set('chart.tickmarks.zerostart', true);
hprogress.Set('chart.units.post', '%');
hprogress.Draw();
OfficeExcel.AddCustomEventListener(hprogress, 'onadjustbegin', function () {console.log('Old value: ' + hprogress.value );});
OfficeExcel.AddCustomEventListener(hprogress, 'onadjustend', function () {console.log('New value: ' + hprogress.value );});
}
</script>