Flex :: Enter Default Values Into FieldContainer?

I am using a Field Container to enter a new Contact information, and I would like to populate some of the fields with values.

I can do this for normal fields like Phone and LastName, but ti does not work for lookup fields like ReportsTo and Account.

This is th code I am using:-

var acc:DynamicEntity = new itemClass("Contact");
acc.Phone="8888";
acc.LastName="Nieddu Srl"
acc.ReportsTo ="0012000000RsJYb"
acc.Account="test"
_createFieldContainer.render(acc)

Is there any way to populate a lookup field with a default value when the field container is called?