How can you check if a resource exists in a resource file by Name?

More info..
I have the students creating a database where there is also a picture of
them in the resource file which matches the name they have typed in the
Name array field. As they click the Next button on their screen we check
the resource file for a picture that matches the name and display it in
a Picture Field, however if there is no picture that matches the name I
want it to clear the picture field or display a default graphic. Get the
picture?

Martin