try this...
SELECT bovd.CusCode, bovd.RecQty from BookOrdVehDetail bovd INNER JOIN VehicleSalesDetail vsd ON bovd.CusCode = vsd.CusCode
WHERE (SELECT sum(cast(bovd1.Qty AS int)) From BookOrdVehDetail bovd1 Group By bovd1.CusCode having bovd.CusCode=bovd1.CusCode)
>
(select count(vsd1.RecNo) New FROM VehicleSalesDetail vsd1 Group By Vsd1.CusCode having vsd1.CusCode=vsd.CusCode)
Happy Coding!
:)