searchlist scope inside loop

hi,
I seem to be unable to test for nested variables in a searchlist from
within a loop: The following snippet loops over the rows, but the if
statement always false.

#for $row in $here
  <tr>
  #for $cell in $row
    #if $varExists('cell.isHeader') and $cell.isHeader


Is it impossible to use $varExists('loopvar.subvar') or is there any
way to test variables from within a loop?

thanks,
--Tim Arnold

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