You've fallen into a trap carefully crafted by the product management
team at Microsoft to lure newbies.

That nifty thing in your table that has a combobox on it is a Lookup
Field.  They are to be avoided at all costs.  They will inevitably get
in your way as you try to actually do useful things with your Access
application.  For further info/justification please visit
www.mvps.org/access

Then re-design your tables and relationships to accurately represent
what you want to happen.

They particularly suck in people who will be entering data directly
into the tables and trying to get Access to behave like a spreadsheet.
Don't require your users (including yourself) to enter data in tables.
Provide Forms instead.

Lookup tables are good.  They are normal tables used to provide lists
from which things can be selected via comboboxes.

Lookup Fields are evil.

HTH

Is the Company name unique within the Pipeline table? Is it the Primary Key of
the Pipeline table? If not, what is?

I'd suggest that the Participants table should simply have a CompanyID field
which uniquely identifies a company. This *could* be the company name, but
company names aren't really good choices for links: they aren't necessarily
unique; they can change over time (Ever hear of Enco? How about Exxon?), and
they tend to be long compared to a 4-byte long integer.

That would let you use a Form based on the Participants table, with a very
simple combo box - no subform, no code, no nothing - bound to the companyID
field.

            John W. Vinson [MVP]