Microsoft Office Mailmerge expert needed

I need someone who can create an excel Data source and Word letter template.

I work for an umbrella company and we have a number of brands under our umbrella.

We need to send letters to customers who have products across all our brands.

I have managed to create a standard letter template that I am happy with. I have also made an Excel document (data source) that I am happy with except for one issue:

I want to add a column in excel that says “Brand”.

Each row may have a different brand; for example customer 1 may have a product from Brand “ABC” and customer 2 has a product from Brand “DEF”

I then want the word document to incorporate the correct letterhead for the respective brand.

The letterheads I have are saved as PNG files but I can’t seem to get the letter generated with the branded letterhead.

The only way i can think of doing it is by making a number of branded letter templates and doing the letters one brand at a time but this seems too fiddly.

Please can someone help, or at least tell me if what I’m asking is bot possible.

Many thanks