I have a database of "artefacts".

An Artefact has a "Main Type"...and a "Sub Type"
e.g with "Main Type" = "Document"
"Document" has "Sub Types" e.g. "Book, Magazine, Newspaper, Certificate,
etc...

I want to let the user select the "Main Type" of an Artefact
and then, they need to be able to select from a "Sub Type".

Eg. If the Artefact "Main Type" was a "Video" they could only
select "8mm Film", "Tape", "DVD"

How can I arrange a Form so that the relevant "Sub Type" is
available from a Drop down menu when the "Main Type" has been chosen.

Thanks

Charles W.