calculating profit in sproc

Hi I am quite struggling to work out how to calculate profit in stored procedure.
The problem is
I have the table:
share name / transaction date/ is it buy or sell / no of shares bought or sold /total cost

I need to calculate how much profit was made on sold shares
The problem is that I need to always assume that you sell shares which were bought first first.
So if I have in chronological order:
tesco buy 50 £200
tesco buy 40 £100
tesco sell 55 £600
profit is
costtobuy of 55 shares: 50 shares at £200 + 5 shares at (£100/40*5 =)£12.50 = £212.50
profit = £600 - £212.5 = £387.50 (too good to be true)

my plan was (if it is too confusing please ignore it and just read the part above)

1 to work out no of shares sold and total cost of sold shares
so
select sum(no of shares) as nosold ,sharename where transaction = sell and sharename= @.sharename return noofshares
select sum(totalsold) as totalcostsold , sharename where transaction = sell and sharename = @.sharename return totalsold
now i need to loop through buys to work out cost to buy of number of shares sold:

so i need to loop through a table which would have buy transactions only(share name, nobought, totalcost) and check what was the cost to buy of this number of shares:
@.nosold(from above table)
@.sharename

output totalcosttobuy = 0

if(nobought = nosold) totalcosttobuy = totalcostobuy + totalcost
retrun
else if (nobought>nosold)totalcosttobuy = totalcostobuy + (totalcost/nobought)*nosold
return
else if( nobought<nosold)totalcosttobuy = totalcostobuy + totalcost
nosold = nosold-nobought (go back to beginning of if)
where sharename = @.sharename
group by sharename

Well I need this if statement to loop through the rows in the table how can I do that?
Then I can do profit = totalcosttosell - totalcosttobuyyou can use cursors or insert the records into some table variable with autonumber and loop through..etc..hope you get the idea ?

hth|||ok i have to read on cursors, have not used them yet ,do you mean to use them inside the sproc?
2nd option do you mean I have trans id as autonumber and say
@.transid
@.totalcosttobuy
@.nosold
...
for(@.transid = 1, @.transid++, @.transid<=countofrows) {
if....
else if...
else
where transid = @.transid}

or something of that kind?|||there is no for loop in sql server. so you can use while loop. if you google for 'alternative to cursors + sql server 2000' am sure you can find plenty of articles...

hth|||ok thanks