updating a reciprocal blast file

I have a large reciprocal blast file that contains 3 proteomes.  I'd like to integrate another proteome for downstream clustering.    I imagine a command-line script that takes as input the new proteome in fasta format, the directory of the the old proteomes in fasta format, and the pre-existing reciprocal blast file, and then performs the proper blasts and updates the pre-existing reciprocal blast file accordingly.  I am using blast locally and the downstream processing is done by OrthoMCL.  I assume this has been handled before, but I can't track down the code.  If anyone is familiar with a pre-exisiting script or has pertinent advice, I'd be much obliged.

Justin