How to RMA normalize microarray expression data only without the CEL files?

Hi.

I have used getGEO function to get several related microarray datasets, extracted the expression values of each and merged them. Now I have the expression values, with geo accessions as columns and probe sets in rows. I want to do RMA normalisation with oligo package, but I cannot as not all CEL files are available for creating an affybatch object. Is there any other way for RMA normalisation?

Thank you in advance.