i have the folling formula, but excel doesn't seem to accept it

=IF(Leave!E5="A","A",IF(Leave!E5="I","I",IF(Leave! E5="S","S",IF(Leave!E5="L","L",IF(Leave!E5="T","T" ,IF(Leave!E5="R","R",IF(Leave!E6="A","A",IF(Leave! E6="I","I",IF(Leave!E6="S","S",IF(Leave!E6="L","L" ,IF(Leave!E6="T","T",IF(Leave!E6="R","R",IF(Leave! E7="A","x")))))))))))))

i need to have all those letters for each of the 5 cells being referenced...
currently using Excel 2000 9.0.6926 SP-3.

if there is a limitation.. how do i get around it ?