Consolidate data from different worksheets with final information coming from a combination of the worksheets

Hoping for some help on a problem I can't wrap my head around. I need to consolidate some information from 12 different tabs (one data pull per month) into one worksheet with some of the data needing to be overridden and some needing to stay. With the most recent pull of the data not necessarily being the information I want showing, I'm not sure how to proceed. I'm trying to find a way to create this and pass it along to someone else to just load data and it automatically puts out the result I'm looking for.

For instance, I pull information from my system in January for the entire year (broken into monthly buckets) and all of that is perfect. My second data pull of the year in February isn't so clean. I need to see the numbers from January on any of the January data (because it zeros out in February in my system) but everything related to February through December needs to be from the most recent data pull. Third pull of the year in March, I need to see the numbers from January and February for the January and February data and then need the new info for March through December. Basically, by the time December rolls around, I need data from all 12 sheets. Hopefully this makes sense.

Any thoughts on how I can accomplish this in Excel?