Infocube filling via Lookup logic

Dear Experts,

I am able to fill the required key figures using end routine into the final cube with an end routine from my look up DSO but I am not able to fill a characteristic into the Infocube from a look up DSO as the system is not allowing me to write an end routine for the same. Can you please suggest what is the reason behind?

My flow is :

DSO1-----Transformation-----------> Infocube
|
/ \

LookupDSO1 Lookup DSO2

(Keyfigures) (characteristic)