To get the values of the additional columns in the combo list you need the
Column property of the combo.
You need to be sure that when the use chooses a value for DealerID that you
save the value of ClearingHouseID at the time of choosing. To do this you
would have fields in the table underlying the form that are updated based on
the values in additional columns of the combo when the user selects a
DealerID . The controls displaying ClearingHouse would need additional
lookup as you would want to display the string ClearingHouse not the ID.
You would probably base the form on an updateable query, see also
autolookup. You would be saving ClearingHouseID in the underlying table,
not the string, to eliminate update anomalies where a clearing house changes
its name, for example. Of course if you want to keep all the history that's
another design altogether.
David