Rowsource is a property. In the property sheet you specify a table or query name, or a sql statement, or as you seem to be talking about - a Value List. A combo with no rowsource will show nothing, so you're not really talking about having (or not) a rowsource; you're talking about what the rowsource is.
EDIT - as long as you're on a learning kick, maybe you should play around later with the listbox idea I gave. It's a common way to perform multiple option selections.
EDIT - as long as you're on a learning kick, maybe you should play around later with the listbox idea I gave. It's a common way to perform multiple option selections.