Function vigenere($t,$k,optional $d) 
 DIM $j,$r,$,$p,$o,$y
 
 For $j=65 To 90 
  $=CHR($j)+$+CHR($j+32) 
 Next 
 $p="0123456789"+$ 
 
 For $j=1 To Len($t) 
  Do 
   $=Left($k,1) 
   $k=Right($k,-1)+$ 
   $y=InSTR($p,$) 
  Until $y 
 
  $=SubSTR($t,$j,1)
  $r=InSTR($p,$)
  $o=IIf(0<InSTR('! ? . ',$+SubSTR($t,$j+1,1)),-1,$o+($=' '))

  If $r 
   $=62-(UCase($t+$k)=$t+$k)*26 
   $=SubSTR($p,1+($+$r+(2*($d=0)-1)*($y-$o-2)-1) mod $,1) 
  EndIf 
 
  $vigenere=$vigenere + $ 
 Next 
 
EndFunction