Tranfereing data between two databases

I have two companies running two differenct databases: One biz is web based the other is brick and morter. Some of the products that I sell on the web are sold in the (brick and morter)store, but the inventory is tracked from the web . So I have been ringing up the items on an other POS linked to the web database, but I was wondering if I could ring the items up on the front (brick and morter) DB and then track that and then transfer the quantity sold information to the web db... Any ideas? Thanks Brent