In essence that's what I have done.. my program is automated so I used the account values endpoint that pulls up what you see as the account management window. I grabbed cash balance and net liquidity, and save it to a csv. When I run my program it finds the csv, and the static snapshot, of the cashbalance and netliquidity as it was before the market opened.Why don't you just look at the previous day's closing balance, from the statement?
KH
during the day if the system buys cash balance goes down.. I have a rule if i spend beyond a specific amount the system shuts down.