Cumulative Sum

Hi, and welcome to the forum.

I don't know of an inbuilt Sigma type function in standard Excel, but no doubt a user defined function (UDF) in Visual Basic could be written. Before doing that though does the following worksheet solution help.

In A2 enter your x constant, in B2 your a constant and in C2 =Max(A5:A104)

In A5 to A14 enter your n numbers starting at 1 and presumably incrementing by 1, ending in 10. Now in B5 and copied down enter

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and finally in B4 enter =Sum(B5:B104)

If that gives you what you're looking for and you prefer a UDF solution, then post back.

Regards

Thanks for the swift response,

one quick quible, your code;
=(((1-$A$2)^A5-1)*$A$2)*$B$2

is misfortunatly miss a pair of brackets around the power (A5-1) which lead me to be highly confused as to why (what i thought were) identical formulas kept giving me highly diffrent answers. But none the less, a quick fix and thats to you i now am up and running. I must confess i had totally forgotten about the max command, which is allowing me to produces the extra lines wonderfully quick.

Whilst it would be nice to a Sigma command, its not entirely vital, just one quick question. Say i have the spread for the next 30 values or so, but i just want to look at the sum of the first say 12, what would the formula to sum the first "x" (12) cells in the row (starting from B5) where x can be selected or typed into a diffrent cell?

Again thanks,
Fraser.

Hi,

I realised that the =Count() in c2 wasn't actually being used in the sum formula. If you use c2 to hold the variable n, then in B4 use

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Rgds

Wonderful!

Thanks for that and have a good New Year!

Regards,
Fraser.

Hi Fraser,

Thanks for the feedback. Please mark the thread Solved and if you wish rate the answer with the 'scales' icon. Have a happy NY.

Rgds