Weighting Costs Across Multiple Months
 

I have a budgeted amount of cash for a certain cost in a budget. For
example; $100,000 for the construction of a building. This amount can
be spread over as many as 60 months or it can be used in only 1 month.
I already have an equation that finds the beginning month and total
months and divides the amount equally amongst the months. The
assumptions I am using look like this:

Amount: $100,000
Beg Month: January-2008
Total Months: 5

My equation essentially finds the beginning month in the header row and
then divides the amount by the total months. So in this problem, it
puts $20,000 under the months of Jan-2008 thru May-2008 for a total of
$100,000.

My problem is that I would like to be able to "weight" the costs
either the front or the back. In other words, instead of having the
costs divided equally, I am trying to figure out how to add in another
assumption that would allow me put more of the costs in the beginning
months or the ending months.

I have an Excel Add-On called Xnumber that does this, but the problem
is that I have to share this spreadsheet with multiple users and many
users don't have the add-on or are not savvy enough to figure it out.
Is there a formula within Excel that I can write to avoid the add-on?
I am familiar with financial modeling and I think this is more of a
statistical problem. Any comments or suggestions would be most
welcomed. Thank you for your time!