Custom function

Custom function

I have 2 applications and 2 separate forms in the 2 applications. I would like to create a custom function in one form in 1 application to populate a field in the other form in the other application.

Application 1: RAMS
Form: Profile
Field: Airstrip_Name (Text field)
Field: Amount (Currency)
Field: Agreement (Yes/No field)

Application 2: DDA Reports
Form: Expenses
Field: Airstrip (Lookup field)
Field: MOA Amount (Currency)

I would like the functions to insert or update the Airstrip and MOA Amount in Application 2 the exact values from application 1 only if the Agreement field in Application 1 is set to Yes. 

I am new to functions and hope someone helps me out.

Thank you

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