I think I understand what your asking.  But I think you have your startbet and target reversed in the comment above.  (not the code).  first you need to save your balance.  I created savebalance in the init section (before the dobet function).  I'm setting it equal to balance, which is a special variable that the bot fills in.  So in theory we should now have the balance before any bets are placed.  In reality you should issue one bet from the bot before starting your script.  Then balance will be correct.  But even if you forget it will correct itself pretty quick. 

   now that you have your initial balance, you only need to check for the target in the win path.  IE you can't reach your target on a lose.  so we can add another if statement before you set nextbet.  This checks and if the current balance minus the saved balance is greater then your target, save the new balance and reset the bet to the base.  if you didn't reach the target, increase your bet. 

   here is the code.