How to match a pattern with VbScript regex in InstallShield?

Question

I'm using VbScript object to do pattern matching but I'm kind of stuck how I need to escape characters in installscript.

I want to check if a string contains one of following characters: /@()='"&

The pattern in next snippet "[\\\/@()='"&]" doesn't do what I want. \ and / are not matched.

// Following characters not allowed: \/@()='"&
if (MatchPattern(ThePassword, "[\\\\\\/@()='\"&]", FALSE) != 0)
then
  return FALSE;
endif;


function NUMBER MatchPattern(Source, Pattern, IgnoreCase)

  OBJECT RegEx, Match;
  NUMBER Result;

  /* -------------------------------------------------------------------------------------------------------------- */

begin

  try
  set RegEx = CreateObject("VBScript.RegExp");
  catch
    MessageBox("CreateObject Failed - "+ Err.Decription, SEVERE);
    return 0;
  endcatch;

  if (IgnoreCase)
  then
    RegEx.IgnoreCase = 1;
  endif;
  RegEx.Pattern = Pattern;
  RegEx.Global = 1;   //set to 1 to find all matches in the string
            //set to 0 to find only the first match

  try
    set Match = RegEx.Execute(Source);
  catch
    MessageBox("Pattern matching failed - "+ Err.Decription, SEVERE);
  endcatch;

  Result = Match.Count;

  return Result;
end;