IsWin 1.3  Is the specified file a Windows GUI program?

  IsWin C:MyProg.Exe
  If ErrorLevel 3 GoTo Problem
  If ErrorLevel 2 GoTO IsForWin32
  If ErrorLevel 1 GoTo IsForWin16
  Goto IsForDos

In debugging you might just use to view the errorlevel result.

echo %ERRORLEVEL

Copyrighted, but may be freely distributed and used for
any purpose except military. Works on EXE, COM and DLL
files. MASM source included. Version 1.3 adds detection for
PKLite DOS exes and Win32 exes.