I have a master excel sheet,abc.xls and I need it to refer to columns found in 2 other csx files:def.csv and ghj.csv.I tried using the VLOOKUP function:

=VLOOKUP(F2,[def.csv]def!R2C15:R439C15+[ghi.csv]ghi!R2C9:R1248C9,1,FALSE)

where F2 is a column in abc.xls and R2C15:R439C15 are the rows referred in def.csv and R2C9:R1248C9 are the rows referred in ghi.csv.However,when I tried this formula in the master copy(abc.xls),it returns a #VALUE! error.As I am not too sure on how to refer to multiple external csv files,could anybody guide me on how to modify this formula?