Is there any way to connect to a view with a pre-defined fileter.

I have a table users and a table customers, with no relationship. I
have x-joined joined these to make a view CustomerLetters for users to
create personalised letters to customers. This view contains every user
with every customer - a lot of records.

When the user connects to mailmerge they have to filter recipients by
user to just select themself, then filter by customer for the account
they want, then run the mail merge on a single record.

Is there any way to automate the first part by passing the user id to
the view before bringing the full list of recipients onto the client?

Thanks
hals_left