as for rangeToolTipTemplate option, I want to do a sum or subtract calculation between endvalue and startvalue variables.
For example, endvalue - startvalue = finalresult like ${item.startValue - item.endValue}
<script id="rangeToolTipTemplate" type="text/x-jquery-tmpl"> <div class='ui-lineargauge-range-tooltip' > <font color='${itemBrush}'> ${item.name} : ${item.startValue - item.endValue} </font> </div></script>
Another possible solution would be to override fireTooltip inernal function of the gauge as it is shown in the jsfiddle below:
http://jsfiddle.net/jj3gdyLL/28/
If you want you can log a product idea about tooltip events in the gauge at http://ideas.infragistics.com, the Product Ideas site allows you to suggest new product features, new functionalities in existing products and controls, and even request new controls and products altogether.