Scoring spreadsheet that needs to reset to zero if score goes negative

I am trying to create a scoring spreadsheet for a game. In this game if you fail to score three turns in a row you lose 1000 points. However if that takes you score into a negative number then you score simply goes to zero and you start scoring again from there. The spreadsheet has 20 rows for the 20 turns for each player. At the top it has a running total. It is this running total where I am stuck. I started off using a simple SUM formula to add up the rows in the column. eg. 100+300 +400 gives the running total of 800. Problem is that if that player fails to score for the next three turns they get -1000 points so their score would return to 0. Only points scored from there on would be counted in the running total, so the sum of the whole column no longer applies. Any ideas out there?