AS355 C of G
I got my psion for just for that purpose - I think I paid £10 from fleabay about 18 months ago, and yes, the programme was loaded for me by one of the engineers at Macs. Worked really well, but now we use the same system as Bertie Thruster described.
I think you might also find PACO will soon come up with a link to some programmes he has written - or you could try a pm to him.
QOS