p910i - contact detaiuls - move to SIM card?

Hi folks, I have a p910i and it syncs the contact details with my PC. I
have recently bought another handset and want to move the (or some of
the) entries onto the SIM card so I can use them on the other handset.

Can anyone tell me if this is possible and if so, point me how to do it?
I don't see anything obvious...

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jeremy