Thanks, I think this will be easier to use than biomart. Although I'll probably go ahead and use biomart as a "double check"/control.
Do you know if TxDb.Mmusculus.UCSC.mm9.knownGene contains RefSeq or Ensembl genes? I also use BSgenome.Mmusculus... instead of TxDb.Musculus... Are they the same? (nvmd, BSGenome didn't install on my R. TxDb did I guess TxDb is an older version?)