Prepopulate Preferred Callback Number on HR Workspace > Create Case

[shawnduster]

We have added logic to our individual case forms in HR Workspace to capture a Preferred Callback Number.  Further, we have logic that looks at five different fields from a mix of sys_user and hr_profile and pre-fills the field with the first non-blank value.  The field remains editable in case the caller wishes to use a different number. 

The above logic is working fine, but for call flow purposes, we'd like to move the Preferred Callback Number earlier in the call.  Specifically, we'd like to put it on the Create Case form and have it similarly prefilled but allow it to be overridden.  I know how to add the field to the Create Case form, but I am not sure how to trigger the logic that prepopulates based upon Opened_for.  If Opened_for changes on the Create Case form, the pre-filled value should  also be recalculated.

I am not a developer but I can do a lot through config, so I can grasp concepts pretty well.  I asked our platform developers, who haven't done a ton with HRSD, if they knew how to do it but didn't get very far.  I am hoping that if you can point me down a path that I and/or my developers can figure this out.  We are running Vancouver if that matters in terms of how to do this.  

The attached image is using Guest for illustrative purposes only so you can see where we put the field where we want the logic to trigger and pre-fill.  Our actual use case would use a real person.

Thanks in advance!