How can I use a java script variable in Where at Lookup Wizard

I would appreciate some help. I am trying to find the way to use a java script variable in Where at Lookup Wizard on ADD Page

This is the case.
On ADD page the user switches Power Units from hp to kW.
Based on selected units, the Lookup Wizard would look up in a table for WHERE 'Units' is = 'Selected units'

Code on Javascript onload Event on ADD page

		
		var ctrlPower_u = Runner.getControl(pageid, 'Power_u');
		var jsPowerUnits = ctrlPower_u.getValue();
		alert ('jsPowerUnits is : '+jsPowerUnits);

Code on Where on Lookup Wizard

" `Units` = 'jsPowerUnits'"

The lookup is returning no records

My first approach was to find a way to pass the variable from Java Script to PHP as a session variable and then use the session variable in the lookup wizard on where statement. Is it possible to pass a variable from Java Script to PHP?

I would appreciate ideas about how to accomplish this lookup
Thank You