Form has two list boxes. List box A has values (from table data1) (list box A).

a b
c d
e f
etc

When I click on a line in list box A I want to display values from display values in list box B from table data2 based on 1st column in list box A. That is display values in list box B from table data2 only if there is a corresponding values for the field in column 1 of list box A (i.e. a, b, c, ...). It would be useful if when I start up it displayed the corresponding values in table data2 for the value a. Thus what I want is when I start it displays

a f
c d
e f

for value a it might display (list box B)

g h l
i j k
etc

and for value b it might display (list box B)

l m n
o p r
etc

If there is no match data in table data2 then list box B should be blank.

I hope this is clearer.