Reporting YTD results every quarter

Hello,

I manage a large excel database containing environmental emissions data (data reported weekly/monthly for sever stations located accross a large "site"). Each datapoint in the database is expressed as a rate (amount/time e.g., kg/month)

Each station has a limit (guideline which should not be exceeded) which is also expressed as a rate (e.g., kg/month).

Every quarter, I need to report our performance. The measure used is sum of all emissions for the entire site to-date, expressed as "% of the limit". For example, for Q1, I first need to take each data point and divided it by its respective limit (*100), them sum all data points from January to March for all stations. For Q2, I need to do the same thing, but from January to June (year-to-date).

I have attached an example spreadsheet containing a smaller but similar database. I need a formula (or series of formulas) that will give me my reportable value for each quarter.

There are probably several ways of doing this, I'm open to suggestions. I'm still a novice when it comes to excel...not sure whether I need to use array formulas to do this. Your help will save me a lot of time (and money)

Notes: "<" flags and blank rows can be ignored (but not removed)

Thanks