using VB in excel

[dziw]

just wondering if anyone can point me in the right direction for help using vb functions in excel, i want to program a summation function of 1 to n values using a for loop and want to make the vb function read numbers from a cell in excel and use them to add values together, any pointers?

thanks

[MrShorty]

put "Excel user defined function" into your favorite internet search engine and have fun.

[Mallycat]

You don't need a function to do this. There is a mathematical formula as follows:

= n(n+1)/2

Matt

[MrShorty]

Good, Mallycat. That works for f(n)=sum(i=1 to n)i It's been too long since I've done those kind of derivations, so I couldn't figure out a shortcut for the actual formula dziw is using. In his other posts, the summation he's using is f(n)=sum(i=1 to n)(A^-i). Are you aware of or could derive a simple shortcut formula for that one?

[Mallycat]

It's been too long since I've done those kind of derivations,

Me too actually. I had to fill a stack of cells with running data and work it out. It took me back! As for this new formula, what is the A all about. Will the answer always have an A in it?

f(n)=sum(i=1 to n)(A^-i)

[MrShorty]

I don't know what A is, other than some constant. The samples he gave were A~1.05 and A=1.5. I don't know if A will always be between 1 and 2 or 1 and 1.5 or what A represents.