Is it possible to set the criteria in my form based upon an unbound text box where multiple items are entered?

I have a list box that when items are selected it adds them to the text box i.e. if someone selects apple and pear from the list box the value of the text box is:

Apple Or Pear

If one or no item is pickedthen everything works as planned, but if multiple items are selected no records are returned. I beleive this is due to the query interpreting my criteria as:

"Apple Or Pear"

which would as expected not return any records. Where my problem lies, is how do I get around this and is it even possible?