not that i know of, because that combo box represents a single field which
implies a single value.
but why do you want to do this? is it to narrow down records? i know at
this access page there is a tutorial to base one combo box on another, which
might do what you want:
http://office.microsoft.com/en-us/FX010857911033.aspx
also if you're trying to get to a record you might try the 'filter by form'
function.
but this is all just guessing what you're after.
hope this helps.
-ih