Horseracing data question

Hello folks – hope you can help me out. In the attached spreadsheet I've worked out the profit and loss made when laying (backing against) each horse in UK racing in 2017 under certain circumstances, in column S.

Each horserace has an identifying number from Betfair, EVENT_ID in column A

The range A2:A11 is 128931852, the 12:25 PM at Lingfield, 31st December
A12:A23 is 128931857, the 12:55 PM at Lingfield, 31st December

and so on.

So what I want in column T is a formula that will give me the total profit/loss for each race in the final cell so that would be T11 for the 12:25 PM at Lingfield, T23 for the 12:55 PM at Lingfield.

How might I do that? Any help very appreciated.

Cheers