; Define the Old and New words
$Old = Oldword
$New = Newword

; Enumerate the list of files.. either from a fixed list (shown below) or using the DIR command
$aFiles = 'File1', 'File2'
For Each $File in in $aFiles
  ; Load the file into an array. Use the FileIO() UDF
  $aData = FileIO($File, 'R')

  ; enumerate the file and replace any occurrence of the word
  For $Ptr = 0 to UBound($aData)
    $aData[$Ptr] = Join(Split($aData[$Ptr], $Old), $New)
  Next
Next
; Write the updated file back
$aData = FileIO($File, 'W', $aData)