Function Vigenere($a,$b, optional $c)
 Dim $t,$u,$i,$j
 $t='0123456789ZYXWVUTSRQPONMLKJIHGFEDCBA'
 $u='abcdefghijklmnopqrstuvwxyz'
 
 ;remove wrong chars in key
 For $i=1 to Len($b)
  If InStr($t+$u,SubStr($b,$i,1))
   $j=$j+SubStr($b,$i,1)
  EndIf
 Next

 $b=$j
 
 ;check for lowercase in string/key, if so expand tableau
 $j=Len($a)+Len($b)
 For $i=1 to $j
  If InStr($u,SubStr($a,$i,1)) OR InStr($u,SubStr($b,$i,1))
   $t=$t+$u
   $i=$j
  EndIf
 Next
 
 ;double the tableau
 $t=$t+$t
 
 ;make the key larger than the string
 While Len($b) < Len($a)
  $b=$b+$b
 Loop
 
 For $i=1 to Len($a)
  $j=SubStr($a,$i,1)
  $u=SubStr($b,$i,1)
  If InStr($t,$j)
   If $c
    $j=SubStr($t,InStrRev($t,$j)+Len($t)/2-InStrRev($t,$u)+1,1)
   Else
    $j=SubStr($t,InStr($t,$j)+InStr($t,$u)-1,1)
   EndIf
  EndIf
  $vigenere=$vigenere+$j
 Next
 
EndFunction