How to store ID on list box but show related data

[Clarionchanger]

I have 2 tables one, Contacts, primary key ContactID this table contains names, addresses etc and one group called Form primary key Form ID, foreign Key Contact ID. I want to store the related contact ID in my form but display firstname ad surname from Contaacts list. This works fine when I am selecting name. List box shows 2 columns with correct data but when I recall the form after making other entries it only displays the firstname. The correct ContactID is stored. Why does this happen.
If I can get this working I would like to concatenate the Firstname and surname to make it more readable but don't know where to begin.
This is my first attempt at an Access database and am finding it very confusing after my other pure database (Clarion). Your help is appreciated.
Thanks Pete.

[June7]

You have a table called 'Form'? Form is a reserved word. Should not use reserved words as names.

List or combo box RowSource:

SELECT ID, Surname & ", " & Firstname FROM Contacts ORDER BY LastName, Firstname;

ControlSource: the field in destination table
ColumnCount: 2
BoundColumn: 1
ColumnWidths: 0";2"

[Clarionchanger]

Thank you June7. Very helpful. BTW I dont have a table called form and the database is much larger than indicated I thought this was the simplest way to describe the problem. Although I did not know Form was a reserved term in Access so I have 2 problems answered.
I'm sure i will be back
Pete

[June7]

It's a fairly long list, review http://support.microsoft.com/kb/286335