CountUnique Based On Count of Another Table

Hi All,

I have 2 tables which is DeliveryOrders and DeliveryOrderItems linked with column "DO Number", now I wish to get the total number of Delivery Order without contains the DO items with "Assembly" item type. I tried to use the following formula:

=NL("CountUnique","DeliveryOrders","DO Number","DeliveryDate",E$15,"DO Number","PD*","=NL(""Count"",""DeliveryOrderItems"",,""DO Number"",NF(,""DO Number""),""ItemType"",""Assembly"")","0")
But I got the #VALUE! error indicate that "The value used in the formula is of the wrong data type". In this case I'm not able to use Link= or inner NL because I need to check the number of DO with its items with/without the given item type.

Hope can get the advise from your guys, thanks!