Dependant Dropdown

I have Three tables
Photos Fields : fldbrand , fldsupplier , vendor_number , supplier_number
Brand_Supplier_Data Fields : fldbrand , fldsupplier
Supplier_CodesFields : fldsupplier , vendor_number , supplier_number
In the Photos edit page I have fldbrand setup to autofill fldsupplier from Brand_Supplier_Data

What I need to due is autofill _vendornumber and _suppliernumber which are not in the Brand_Supplier_Data Table above.
The 2 field names above are the same name in the Photos Table and Supplier_Codes Table

So I set supplier_number and vendor_number to be dependant upon fldsupplier.

I am only using the edit page in the Photos table and the data is copied from another table outside of this discussion.

When I open edit page the fldbrand data shows , the fldsupplier shows but the vendor_number and supplier_number are blank..

If I move up the dropdown to "Please Select" then select the only fldsupplier data that is there it fires the call and fills in vendor_number and supplier_number.That I want.
My problem is how do I get the dropdown of the fldsupplier to stay at "Please Select" so the user can then select fldsupplier and fire the vendor_number and supplier_number automatically. Seems since the fldsupplier is already filled in there is nothing to fire the fields unless I go to "Please Select" and then select fldsupplier data ; which then fires the 2 fields .