use Win32::API;

my $DataToEncode = "Test1 Test2 Test3";

my $return_sring = undef;

use Win32::API;
  $function = Win32::API->new(
      'IDAutomationDMATRIX6', 'FontEncode',['P','N','N','N','P']
  );

   my $string =  $function->Call('FontEncode');
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There are still some inconsistencies in the above code - and these inconsistencies may be preventing the thing from working (there might also be Win32::API bugs that mean it's never gunna work anyway).

I think you still need to specify the return type in new:

  $function = Win32::API->new(
      'IDAutomationDMATRIX6', 'FontEncode',['P','N','N','N','P'], 'P'
  );
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You could also try the 2 following renditions:

  $function = Win32::API->new(
      'IDAutomationDMATRIX6', 'FontEncode',['P','N','N','N','P'], 'P',
+ '_cdecl'
  );
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and

  $function = Win32::API->new(
      'IDAutomationDMATRIX6', 'FontEncode',['P','N','N','N','P'], 'P',
+ '__stdcall'
  );
[download]

Since FontEncode takes 5 arguments, Call() also needs to be given 5 arguments - a string, an int, an int, an int, and a string (in that order):

my $string =  $function->Call($str1, $n1, $n2, $n3, $str2);
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Finally, $string may need to be large enough to accommodate the return string:

my $string = '' x 500; # Big enough ?
$string =  $function->Call($str1, $n1, $n2, $n3, $str2);
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Without access to the dll it's hard to provide good assistance. If you can't get anywhere with it using Win32::API, then VB might be your best approach.

XS/Inline::C would also be options - and they provide excellent milage. I far prefer Inline::C over Win32::API, any day. However, for that to be an option, you also need the relevant header (.h) file and import lib (.lib) - as well as a Microsoft C compiler. (Actually, MinGW usually works fine, too - and doesn't even need the import lib. But I don't think you can use MinGW where COM is involved.)

Cheers,
Rob