Check multiple conditions for proper value

In my attached workbook... I want to sum TRADES U2. I first need to check the value of TRADES A2 to use the appropriate numbers from INSTRUMENTS.

I have attempted to use IF(OR and IFS. In both cases, I receive an error, either 'too many arguments', or 'too few arguments'.

As an example, using IFS...

=IFS(A2="NQ","((((G2*I2)+(J2*K2))-((N2*O2)+(P2*Q2)))*INSTRUMENTS!D4)-INSTRUMENTS!I4",A2="MNQ","((((G2*I2)+(J2*K2))-((N2*O2)+(P2*Q2)))*INSTRUMENTS!D5)-INSTRUMENTS!I5",A2="ES","((((G2*I2)+(J2*K2))-((N2*O2)+(P2*Q2)))*INSTRUMENTS!D6)-INSTRUMENTS!I6",A2="MES")",((((G2*I2)+(J2*K2))-((N2*O2)+(P2*Q2)))*INSTRUMENTS!D7)-INSTRUMENTS!I7")

In this case, TRADES A2 = ES, so I need to use the numbers in INSTRUMENTS Row 6...

((((G2*I2)+(J2*K2))-((N2*O2)+(P2*Q2)))*INSTRUMENTS!D6)-INSTRUMENTS!I6

By itself, this works. However, I cannot get it to work from within an IF(OR or IFS formula.

Thoughts?