Too few arguments / formula is missing an open/closing parenthesis

[KCowan]

I copied the formula from a similar one in another thread here, but keeping getting either "too few arguments" or "closing parenthesis". Help? IFERROR(IF(I3="AVG",VLOOKUP(A3,'Master Table'!$A$3:$Z$3537,22,FALSE),IF(I3="P1/CY Avg",VLOOKUP(A3,'Master Table'!$A$3:$Z$3537,23,FALSE),IF(I3="40/60",VLOOKUP(A3,'Master Table'!$A$3:$Z$3537,24,FALSE),IF(I3="30/70",VLOOKUP(A3,'Master Table'!$A$3:$Z$3537,25,FALSE),IF(I3="20/80",VLOOKUP(A3,'Master Table'!$A$3:$Z$3537,26,FALSE))))))

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[Fluff]

Hi & welcome to MrExcel.
You are missing the end of the IFERROR, try
=IFERROR(IF(I3="AVG",VLOOKUP(A3,Pcode!$A$3:$Z$3537,22,FALSE),IF(I3="P1/CY Avg",VLOOKUP(A3,Pcode!$A$3:$Z$3537,23,FALSE),IF(I3="40/60",VLOOKUP(A3,Pcode!$A$3:$Z$3537,24,FALSE),IF(I3="30/70",VLOOKUP(A3,Pcode!$A$3:$Z$3537,25,FALSE),IF(I3="20/80",VLOOKUP(A3,Pcode!$A$3:$Z$3537,26,FALSE)))))),"oops")
Replace the part in red to suit

 

[KCowan]

Thank you, Fluff!

 

[Fluff]

You're welcome.
I've also noticed that if the Value in I3 doesn't match one of the values in the formula, it will return FALSE, to correct that use
=IFERROR(IF(I3="AVG",VLOOKUP(A3,Pcode!$A$3:$Z$3537,22,FALSE),IF(I3="P1/CY Avg",VLOOKUP(A3,Pcode!$A$3:$Z$3537,23,FALSE),IF(I3="40/60",VLOOKUP(A3,Pcode!$A$3:$Z$3537,24,FALSE),IF(I3="30/70",VLOOKUP(A3,Pcode!$A$3:$Z$3537,25,FALSE),IF(I3="20/80",VLOOKUP(A3,Pcode!$A$3:$Z$3537,26,FALSE),"No value"))))),"oops")

Once again change value in red to suit.