Use the combo's After Update event.
Private Sub MyCombo_AfterUpdate()
Dim rst As Recordset
Set rst = Me.RecordsetClone
With rst
.FindFirst "[PrimaryKeyField] = " & Me.MyCombo
If Not .NoMatch Then
Me.Bookmark = .BookMark
End If
End With
End Sub
[PriemaryKeyField] should be the name of the field in the form's recordset
that is the primary key.
The above also assumes that key is a numeric field. If it is not, you will
need to use the correct delimiters for the field's data type.

Signature
Dave Hargis, Microsoft Access MVP
> I have my primary key as a combo box where you can search for the correct
> key. When the user finds the correct key how would I have the rest of the
> data show up below it?