Hi Mitchell,
This formula in C2 calculates the fees owed for all the rows. It does require two helper columns, which you could hide, or move elsewhere if you prefer. I feel it could be done without the helper columns, but I haven't figued that out.
={"Fee";ArrayFormula(IF(B3:B="","",
IF( F3:F -(B3:B*0.3) >= 2000,
0,
IF( ROW(B3:B)=ROW(B$3),
B3:B*0.3,
IF(SUMIF(ROW(E$3:E),"<="&ROW(E3:E),E$3:E)<=2000,
E3:E,
2000-SUMIF(ROW(E$3:E),"<="&ROW(E3:E)-1,E$3:E))))))}
Let me know if this helps.
Cheers,
Gill