Need fore speed...

[Mark Smith]

One approach might be to do this:

   set the itemDelimiter to tab
   repeat for each line L in tData
     add 1 to counter
     put counter & comma after tArray[item 3 of L]
   end repeat

Now you have an array, the keys of which are the pemMass values, and  
the contents of which are item lists of the line numbers with those  
values. You can now do your comparisons to obsMass on the keys, and  
those which meet the criteria will give you a list of lines in your  
original data.

It's still going to be a longish process, though!

Best,

Mark