I have made the following formula in a spreadsheet im working on to find the
amount of packs in a delivery as a percentage ((J48/SUM($J$48:$J$50)*100)
and to proportionate the cost (Cell ref. I48) therefore getiing the anser as
a %age of the cost. (feel free to ask if your lost!)
Here's the formula:
=I48*((J48/SUM($J$48:$J$50))*100)%

Is there a way I can amend this so i can copy this formula for other sets of
data or another amount of numbers (eg $A$1:$A$15)?

Cost Total Packs Cost per Item
649.6 140000 324.80
649.6 84000 194.88
649.6 56000 129.92

Here is an example of what I need. There is more to the spreadsheet but this
is what the formula is based on. This is just 3 lines corresponding to 1
group of data.
Sometimes it can be 2 lines up to around 12. I need a formula that will add
up the packs, get the relative percentage and find that percentage of the
cost. The only problem arises when i have to copy and paste the formula to
relate it to other groups of data as it formula doesn't go to the adjacent
cells as above, they stay in the original cells. Also I have a problem with
the amount of data each time too.

Hope this has been a help