-.js

"The nlapiScheduleScript API consumes 20 units per call. This API is supported in user event, portlet, RESTlet, scheduled, and Suitelet scripts." like @jkabot suggested, you can't do it at the form level (sorry tagged wrong person earlier)

this reply quotes clear indication that you cannot use this in client scripts

One way out would be calling a Suitelet/RESTlet from client script that calls your scheduled script.