Thanks very much for for both of your comments. I think for this script 
Im going to just calcuate on teh fly but try and seperate this code so 
that in the future when i become a bit better with db design I can swap 
it for some other implementation.

Thank you once again!

adam

ps are there any good books on db design which arent product (i.e. MSQL) 
specfic.

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