I have scripted RunFile.bat to open a document in its' associated application, or if there is no association, in Notepad.exe.

The syntax for using RunFile.bat is:

call RunFile FileName \[/WAIT\]


FileName is the file that you wish to open in its' associated application,
like File.doc opening in Microsoft Word, and File.pdf opening in Acrobat Reader.
If no association exists, the file is opened in Notepad.exe.

/WAIT is an optional parameter that causes RunFile.bat to wait until you close the application before returning.
RunFile.bat contains:
@echo off
if \{%1\}

\{\} @echo Syntax: RunFile FileName \[/WAIT\]&goto :EOF
if not exist %1 @echo Syntax: RunFile - %1 NOT found.&goto :EOF
if \{%2\}

\{\} goto no2
if /i \{%2\}==\{/WAIT\} goto no2
@echo Syntax: RunFile %1 %2 - %2 NOT /WAIT.
goto :EOF
set type=N
call :typeOK %1>nul 2>&1
if "%type%" EQU "N" goto BAD
start "" %2 %1
goto :EOF
start "" %2 notepad.exe %1
goto :EOF
for /f "Tokens=*" %%x in ('assoc %~x1') do (
set type=Y