Formula to calculate total values from a mix of progressive actual and forecast data

[heniek00]

Hi Guys! I'm getting frustrated with my indolence in solving the following problem. Hope some smart good people can help me
I have a spreadsheet in which I add project actual and forecast cost on monthly basis. There is around 500 different projects which, obviously, have different duration, start and end months.

What I need to do is to calculate total value of each project and each month based on actuals and forecast

E.g. Project X started in July and ended in October so its total value in September is SUM(July Actual + August Actual + September Forecast + October Forecast). Any ideas what formula could handle that? I've tried to play with SUM(Actuals) and some OFFSET + MATCH functions but never got the right result...

Below is a simplified table for your reference

		Jul-18 Act	Aug-18 Act	Sep-18 Act	Oct-18 Act	Nov-18 Act	Dec-18 Act	Jul-18 For	Aug-18 For	Sep-18 For	Oct-18 For	Nov-18 For	Dec-18 For	Total Act+For
Jul-18	Project X	10						5	5	10	6			???
Aug-18	Project X	10	6					5	6	11	9			???
Sep-18	Project X	10	6	11				5	6	10	8			???
Oct-18	Project X	10	6	11	8			5	6	10	9			???
Sep-18	Project Y			75						70	80	95	82	???
Oct-18	Project Y			75	79					70	82	90	82	???
Nov-18	Project Y			75	79	110				70	82	85	82	???
Dec-18	Project Y			75	79	110	82			70	82	85	82	???

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[Special-K99]

"It's total value in September is

SUM(July Actual + August Actual + September Forecast + October Forecast)"


Nope.

It's total value in September is just

July Actual + August Actual + September Forecast + October Forecast

You don't need SUM(), you're already SUMming them by using the plus sign.
It's like saying (and this happens an AWFUL lot)

SUM(3+4)

It's simply 3+4

You dont need the SUM()

 

[heniek00]

That's a fair comment but still does not answer the question about a formula to calculate those sums for different rows/months.
Anyone please?