character ASCII code in InstallScript InstallShield

I want to keep user from entering character > ASCII 127 in one of the password field in installer.

I googled but didn't find any direct way for this, currently i'm using:

CHAR ch;
STRING ASCII;
NUMBER nASCII;

for nCount = 0 to StrLength(sPassword)
  ch = sPassword[nCount];
  sprintf(ASCII,"%d",ch);

  StrToNum(nASCII,ASCII);

  if ( nASCII > 127 )
    MessageBox("Invalid Character in Password",INFORMATION);
  endif; 

endfor;

Is there any better way to get ASCII code from a string?

First off, I would avoid the conversion to and from string; just compare sPassword[nCount] with 127 directly; InstallScript stores wide chars (16-bit numbers).

As an alternative approach, you might try calling WideCharToMultiByte with the US-ASCII code page (20127). I'm not that strong with InstallScript and am coding without the compiler, so you might have to fix an error or two, but here's the rough idea:

#define CP_US_ASCII 20127
extern prototype NUMBER Kernel32.WideCharToMultiByte(NUMBER, NUMBER, WSTRING, NUMBER, STRING, NUMBER, STRING, BYREF BOOL);

function BOOL IsSafeAscii(STRING szCheck)
    STRING szOut;
    BOOL bReplaced;
begin
    WideCharToMultiBute(CP_US_ASCII,          // only supports characters 0-127
                        WC_NO_BEST_FIT_CHARS, // or maybe 0; disallow turning accented to plain
                        szCheck,              // test string
                        StrLength(szCheck),   // length of test string
                        szOut,                // return buffer
                        StrLength(szOut),     // length of return buffer
                        "?",                  // replacement for unsupported characters
                        bReplaced);           // whether replacement was used
    return !bReplaced;
end;