Using SUMIF to deduct last available values from closures

This is a bit of wacky request and I am still having a tough time trying to describe what exactly I think needs to be done to complete this request. I seems like I'll need a SUMIF on the date, a SUMIF on the company, and then some sort of difference formula to calculate the last available value (that is the part I am currently tripped on on). I have attached a sample workbook of what I am working with. I added some highlighted cells with notes to assist with this request. Any help would be much appreciated!

*attachment feature was not working so I'm going to try a reply

Thanks