VTP mesages through a router

Hi,

I am studying for my CCNP and have not been able to find an answer to a VTP set up on a home lab.

I have 2 switches seperated by a router. I have switch A set VTP server and swicth B set as VTP client but cannot get VLANs to update to switch B.

I have tried setting the router to the same VTP domain, version, password etc and also tried it in transparent mode but still i cant get any joy.

Surely there must be a way?

Thanks,

Mo