converting protein names protein ids and enterz gene ids - (Dec/27/2012 )

I got data from proteomics core (mass spec) they have used protein names (mouse) I have to overlay this data with my chipseq data which has gene names as well as Enterz gene ids.I was wondering is there a tool available where I can put list of proteins around 300- 350 to get enterz gene ids or protein accession ids.

Thanks

you can use BioMart ID converter here http://central.biomart.org/#ID_converter-container