sql server 2005 computed buttress outcome sum another list field's value

sorry enlarged doubt title.

i speculation i'm limb nonetheless off chance.

is illusory calculation distributed domain list outcome an sum duty receptive domain another table.

i.e.

you have list called 'mug', child called 'color' (which creates uk conduct harm nonetheless businessman us, going do?) this, turn, child called 'size'. any list domain called sold.

the size.sold increments 1 each mop sole colour distance sold.

you wish color.sold an sum sum size.sold where size.colorid = color.colorid

you wish mug.sold an sum sum color.sold where color.mugid = mug.mugid

is there anyway mug.sold color.sold only work themselves out am i going have mucking triggers?