Suppose a retail daytrader has a $50k margin account, and let's assume its value stays above that level for the whole day. He wants throughout the day ideally have simultanously 5 positions open, each initially worth about $10k. If a position needs to be closed he closes it and wants to open another one. Now the question: Is there a limit (per regulations etc.) on how many total round-trip trades he can make on the same day? Ie. what happens with his DTBP when he closes a position? Will it increase back to previous levels? Another related question: what is different if that trader were an institutional daytrader?