Indirect function within Vlookup

Hello one and all!

I have the following issue:
I have 2 spreadsheets. 1 Master and 1 Slave.
The slave has a number of worksheets containing sets of data.

The Master collects all this data.

I am using the following formula.

=IF(ISBLANK(VLOOKUP($J97,[Raw.xls]ELTO!$A$2:$R$99,12,FALSE)),"",VLOOKUP($J97,[Raw.xls]ELTO!$A$2:$R$99,12,FALSE))

Where RAW.xls is the slave file holding all the data. (ELTO is the worksheet name)
J97 is the reference cell , and holds data such as Project A, B, C

Now if within the Master file, column I had the word ELTO or something else, hwo do i incorporate this within the formulsa?
The next worksheet I want to use is called Morizz, and so on.

I know I have to sue INDIRECT but unsure where.


Help!


Thanks!