Excel look up values and select most recent year

maynardsAH 

The query will be many magnitudes faster if you use the Usage table (which has already aggregated the usage data), rather than trawling through a massive number of records.  

If you are not worried about whole month, this is a simple query for each 30d period

Usage
| where TimeGenerated between ( startofmonth(now(),-3).. endofmonth(now(),-1) ) 
| summarize GBday = sum(Quantity)/1000 by bin(TimeGenerated, 30d)

Go to Log Analytics and run query

 or to have whole months, maybe this is a start:

union
(
    Usage
    | where TimeGenerated between ( startofmonth(now(),-3).. endofmonth(now(),-3) ) 
    | summarize GBmonth=sum(Quantity)/1000 , min(TimeGenerated), max(TimeGenerated), month = datetime_part("month", min(TimeGenerated))
),
(
    Usage
    | where TimeGenerated between ( startofmonth(now(),-2).. endofmonth(now(),-2) ) 
    | summarize GBmonth=sum(Quantity)/1000 , min(TimeGenerated), max(TimeGenerated), month = datetime_part("month", min(TimeGenerated))
),
(
    Usage
    | where TimeGenerated between ( startofmonth(now(),-1).. endofmonth(now(),-1) ) 
    | summarize GBmonth=sum(Quantity)/1000 , min(TimeGenerated), max(TimeGenerated), month = datetime_part("month", min(TimeGenerated))
)