Query based on multiple parameters - Access 2003

I would like to create a query where the user can input 2 or more parameters
(part numbers), separated by comma and/or space and return information about
that part. I already have a query that accepts one parameter. Is there a
way to do this with more than one?

I have read some posts that say to use a table to serve up the paraments and
the user chooses one or more. However, a particular part or parts may not
yet be in the table as they are new or unknown.

Is there any way to do this without using an existing table but just accept
input from the user on the fly?

Thanks!