Passing the Key in $expand Option

Hii,

Here is my ODATA Service link.

http://XXX:XXsap/opu/odata/sap/ZABC_ORDARRY_SRV/ORDDETSet(Userid='XYZ',Type='36')?$expand=ORDpartSet.

The  Scenario:

By Passing the Work Order type as '36'. I will get the  Order details ( ZORDDATA Custom Table ) and Order Part Details ( ZORDPART table)

For a Single Order . there will be multiple parts. So I use the $Expand to get the  Order part details  ( Work type  will be the Key)

Now If  I the User does not pass the Work type (or value as '' or blank) , I wont get any Part details though I will get other order details from  ZORDDATA table.

Now the Requirement  : I need to Fetch the  Order type from ZORDDATA  and Pass it  to ZORDPART and get part details without directly passing the  Work type field in the ODATA Service,

ie,

http://XXX:XXsap/opu/odata/sap/ZABC_ORDARRY_SRV/ORDDETSet(Userid='XYZ',Type=' ')?$expand=ORDpartSet.