Help with forecasting in query

[dansalmada]

I am trying to forecast 12 months of sale in a query

The only info I have is January Sales and a percentage change for each of the following 12 months.

I multiply that change * january sales to get february forecasted sales. The problem is I can't multiply that new february value * change to get march forecasted sales. I think the problem is since the feburary value doesn't actually exists (it comes out from multiplying) then when March tries to multiply february's value it gets zero as total.

Is this understandable? Please Help!

Thanks

 

[The_Doc_Man]

You are probably using the wrong formula.

You have some choices. If you project Feb sales = 2% more than Jan sales,

Feb sales = ( Jan sales * 2% ) + Jan sales
Feb sales = Jan sales * ( 102% )

then to get Mar sales, you can use:

Mar sales = ( Jan sales * ( 2 months * 2% ) ) + Jan sales
Mar sales = Jan sales * ( ( 102% ) ^ 2 months )

One of these is straight interest; the other is compound interest.

Now... how do you get the "2" that represents the number of months?

Try looking up DateDiff as one possible source, with units in months for the difference between the two input dates.