create subfield picklist from data in a third form

create subfield picklist from data in a third form

Hi,

I have managed to create a dynamic pick list from one form to another 

The form is a Crew booking form that is linked to a crew form that contains the contacts details including the roles they are skilled to perform.

The script is on the crew lookup on user input

//create a picklist based on related crewmember's skills
rolepicklist = Crew[ID = input.Crew].Roles_Available;
Role:ui.add(rolepicklist);

it creates a list of roles available based on the crew persons skills.

My problem is I don't use the Crew Booking form to create the record, the crew booking form sits within a call sheet which will contain lots of other subforms like location and equipment. 

So what I need to be able to do is select the Crew in the crew booking sub form in the Call Sheet and for that sub from to select the roles_available from the Crew form not the crew booking form.

Is this possible? How do I go about it.

Thanks