You make a query for Models that is filtered based upon the criteria in the
open Form combo box   i.e. the user selects Ford in that combo box...

make sure your query returns correctly...

then make a list box or subform or popup form (your choice) that is using
that query as its record source...

if you use a separate form an open it...it will trigger a new query.   if
you use a list box or subform that is already opened  - then you must force
it to requery once the choice of model has been made... several ways to do
that ...use a button or afterupdate event.... search the forms/forms coding
for requery for more on that...