Update a field in one module from a field in another. Can this work?

I’m trying to update any given contracts module with a salesperson from the Accounts module so the proper salesperson gets credit for the sale. I can get it to work when I update the Accounts module, but I would like it to work when I update the CONTRACTS module

I attempted to use workflow with the following:

WorkFlow Module Accounts
Run always
Run on All records

Conditions
Contracts: aos_contracts Contract manager equal to Value _____________ (none)

Action

Modify record

Select Action Modify Record
Record Type Contracts : aos_contracts
“Contract Manager” Field “Sales Person Assigned”

I’ve tried all sorts of things with adding Relationship and going back and forth. Hoping for a better solution than trial and error.

Thanks in advance

Any help with this is appreciated