remember a cells value after you chnage ito something new?

[leeham]

The topic is not very well worded Im afraid..
Hello all
This is something my work has asked if I can help them with and as I cant I figured maybe someone else here could so here goes..

if you look at this screen shot:
http://hgbforum.net/liam/screenshot.GIF

see where it says TOTAL CLAIM THIS PERIOD £190 well the formula to make that total is =SUM(D1324)

now see on the right where it has SUMMARY OF CLAIM and PERIOD 1 £190?
that forumla is just =SUM(D25)

BUT

what my boss wants if possible is that when they change the values in cells D13 to D24 (thus changing the total for cell D25) the summary of claim period 1 cell keeps a value of £190 and then we can make period 2 the value of the newly changed D13 to D24.

Then when it comes time for period 3, change the D13 - D24 values again creating the period 3 total but keeping periods 1 and 2 what they were and so on.

Hope this all makes sense, ive tried my best to explain it. I dont even know if this is possible so thats why im asking here.

any help would be greatly appriciated

Thanks
Liamx