Working out the average score in a column after checking another

Evening,

I am using this formula to work out the average in the column if the value of C17 is in column H

=IFERROR(AVERAGEIFS('VA Predictions'!AA$2:AA$300,'VA Predictions'!$H$2:$H$300,Lookups!$C17),"")

However, I need to adapt the formula so it does this if anything but the value in C17 is in column H, I tried this:

=IFERROR(AVERAGEIFS('VA Predictions'!AA$2:AA$300,'VA Predictions'!$H$2:$H$300<>Lookups!$C17),"")

but no joy, any help would be appreciated.

Many thanks