Is there a Excel formula range to automatically move month on month?

[smooth90]

I am currently trying to use a formula range to automatically move along a column every month based on values up until the current month.
When a new month begins the formula should extend its range to the next new month and extend the sum. Each month ranges up to 4 years worth.

the error seems to be the lookup part not bringing through the values.

=SUM(AY26:FS26,INDEX(R26:FS26,MATCH(CHOOSE(MONTH(K21),DATERANGE),DATERANGE,0)))-SUM(R26:FS26)

Anyone know of a better method?

 

[StephenCrump]

Welcome to the Forum!

The first problem with your formula is that you are using the CHOOSE function incorrectly. If you are looking for a value in a range you'll need MATCH.

The better method may be a SUMIF or SUMIFS, but first you'll have to give us a bit more detail about what you intend your formula to do?