Have ya got somethin like this?
cboMake:
SELECT DISTINCT tblMAKE.makeid, tblMAKE.make FROM qryMAKE;
cboModel:
SELECT DISTINCTROW tblmodel.modelid, tblmodel.model, tblmodel.code,tblmodel FROM tblModel WHERE (tblModel.Makeid=CboMake);
cboMileage:
SELECT Mileageid, Modelid, .... FROM...