I have problem which I can't understand.
I have created DE Class for my database which hold two tables and relation between them.
The code is this:

#DEFINE databasepath "C:\mydirectory\"

DEFINE CLASS CUSTOMERS AS cursor
    alias = "CUSTOMERS"
    cursorsource = "CUSTOMER"
    database = DATABASEPATH + "BUSINESS.DBC"
ENDDEFINE

DEFINE CLASS ORDERS AS cursor
    alias = "ORDERS"
    cursorsource = "ORDERS"
    database = DATABASEPATH + "BUSINESS.DBC"
ENDDEFINE

DEFINE CLASS ORDERS_TO_CUSTOMERS AS relation
    childalias = "CUSTOMERS"
    parentalias = "ORDERS"
    RelationalExpr = "CID_ORDER"
    childorder = "CID_ORDER"
ENDDEFINE

DEFINE CLASS businessDE AS DataEnvironment
    ADD OBJECT oCUSTOMERS AS CUSTOMERS
    ADD OBJECT oORDERS AS ORDERS
    ADD OBJECT oORDERS_TO_CUSTOMERS AS ORDERS_TO_CUSTOMERS

	PROCEDURE Init()
		this.OpenTables()
	ENDPROC
	
	PROCEDURE Destroy()
		this.CloseTables()
	ENDPROC
ENDDEFINE



When I try to create instance of this class:
oDE = CREATEOBJECT('businessDE')
it shows this: "Variable 'CID_ORDER' is not found.'.
and it shows (de)bug on this.OpenTables().

When I remove relation class (ORDERS_TO_CUSTOMERS) creation of instance is OK but there is no relation between table.

What is the problem? Can anybody help me?