Mid Way To Slow Used 7320 Times?

im comparing some datas from 2 arraylists and i need to use something like mid because the last 2 chars of the arraylists().tostring are going to be different and i want to exclude them from the check, basically im using something like this

if mid(arraylist1(i).tostring,1,arraylist1(i).tostring.length - 2) = mid(arraylist2(i).tostring,1,arraylist2(i).tostring.length - 2) then

end if how slow is this into a loop that has to do it up to 7320 times? i checked it on my pc and it semms to work just fine, under 0.3 seconds, but the problem is my pc has 3.6ghz dual core 4gb ram on a windows xp.im more worried about other slower pcs, do you think using that comparison is a bad idea to performance?