adding data to a table from combo box

Hi All,

I have a bit of a problem here.

I have a table "Sponsor" which has fields like "NameofActivity", "Sponsor1", "Sponsor2"....and so on which means that for a particular activity there can be more than 1 sponsor.
I have a form which has a textfield(for activity) and a combo box(for sponsors)....Now what I want is, that for a particular activity(which I type in the textfield), I want to add a new sponsor in the TABLE which is NOT existing in the combo box.

I have been able to add new sponsors in the underlying table but I want to add it against a particular activity.


If anybody is confused about the question, I will try explaining it more clearly.
Any ideas would be extremely appreciated.
Thanks you All in advance.