Re-using the Priority Date with new employer

[rakeshnarayan]

Hi,
I am working with Company A and my I-140 approved on Feb 2013. If I change to Compaby B immediatly and Company A is not revoking my I-140, can I re-use my priority date (PERM applied date)?

I heard about some 180 days cooling period with the employer through which I-140 is approved for priority days re-use. But never seen any legal statement of document.

Can somebody help me clarifying this?

Thanks
Rakesh