SELECT ...
    deltmb.deldt ExpectedDeliveryDate,
    deltmb.inpurc ExpectedDeliveryQuantity
FROM Prod
...
OUTER APPLY (
	SELECT TOP 1 convert(VARCHAR(max), dbo.GetDateO(deldt, 0), 105) deldt
		,inpurc
	FROM DelTmBal d
	CROSS JOIN GetDateHelper
	WHERE d.ProdNo = prod.prodno
		AND dbo.GetDateO(DelDt, 0) > GetDateHelper.NowDate
	ORDER BY deldt ASC
	) deltmb