Vendor primary currency not updating when using workflow

Hello,

I have a simple workflow that creates a vendor record based of the back of a custom record.

There are only 3 fields being populated from the custom record.

1. company name
2. subsidiary
3. Primary currency

When the workflow creates the vendor record the first 2 fields are populated but the primary currency is defaulting to the base currency of the subsidiary.

When in the workflow engine it only gives me the field option of 'currency' no 'primary currency'

Anyone have any ideas?

Thanks