adding new records using a form and a subform

[Karen]

I have a database where I have three tables, Reagents, Prep, Ingredients.
These have a common field, code. Reagents has stuff like code, description,
createdate, etc.
Ingredients has code, rm#, rmdesc, amount. (this would have multiple records
for each code, as many as it takes to list all ingredients)
Prep has code, prepproc, safety notes.

I want to create a form (entryform) to enter a newly created reagent. I'm
okay on the Reagent and Prep tables but I want to use a subform to enter the
records for Ingredients. I get a subform on entryform but when I get to it
in the tab sequence, I can't add records to it.

Any ideas?

Karen