cost element in FRL in obyc

hi all

we have created external service account as cost element and that is mentioned iin transaction key FRL in obyc

so whenever i am doing the GR for subcontracting posting system will debit the FRL account and will credit the GR/IR account

so at the time of Gr system is asking for the co object now thing is that i cant mention the Cost center there as there is no option in migo for that

my query is do we have to create a new account for FRL and that we should not make up as a cost element but then how we are going to pass the expense entry to controlling module from FI

i