Changing worklocation within US for same employer on L1 Blanket Visa

[onlineseek]

Dear Team,

I am currently on L1 Blanket visa. My petition is filed against the city X, CA. However I work from client location in City B, IL. Is it possible to work legally from a different location other than petition city and state? If yes, what is the procedure employer need to follow. Is there any amendement which can be applied to petitions.