Here s what I use:

@echo off

rem there is a tab in the file at the end of the line below
set tab=    
set cmd=javaw -jar libMyProg.jar
set dir=%~dp0

echo Starting MyProg
set pid=notfound

for /F "usebackq tokens=1,2 delims=;=%tab% " %%i in (
    `wmic process call create "%cmd%"^, "%dir%"`
) do (
    if /I %%i EQU ProcessId (
        set pid=%%j
    )
)

echo %pid% > MyProg.pid

The directory is set to the directory that the cmd file is located in. Change dir to alter that. Modify cmd to change which command is run.

If you want a stop.cmd that kills it, it would look like this

@echo off
for /F %%i in (%~dsp0MyProg.pid) do taskkill /F /PID %%i
del %~dsp0MyProg.pid

you can use vbscript, here s an example creating notepad, then terminating it using its pid

strComputer = "."
Set objWMIService = GetObject("winmgmts:{impersonationLevel=impersonate}!\" & strComputer & "
ootcimv2")
Set objStartup = objWMIService.Get("Win32_ProcessStartup")
Set objConfig = objStartup.SpawnInstance_
Set objProcess = GetObject("winmgmts:rootcimv2:Win32_Process")
errReturn = objProcess.Create("notepad.exe", null, objConfig, PID)
If errReturn = 0 Then
    WScript.Echo "Process ID is: " & PID
End If 

WScript.Echo "Ready to kill process: " & PID & "? [Y|y]"
Do While Not WScript.StdIn.AtEndOfLine
   strInput = strInput & WScript.StdIn.Read(1)
Loop
If LCase(strInput) = "y" Then
    WScript.Echo "Select * from Win32_Process Where ProcessId =  " & PID & " "
    Set colProcessList = objWMIService.ExecQuery("Select * from Win32_Process Where ProcessId =  " & PID & " ")
    For Each objProcess in colProcessList
        objProcess.Terminate()
    Next
End If 

save as myscript.vbs and on command line

c:	est> cscript /nologo myscript.vbs

A slight variation on the answer provided by @kybernetikos since it has a parsing issue. Note the line if %%j gr 0 (

@echo off

rem there is a tab in the file at the end of the line below
set tab=    
set cmd=javaw -jar libMyProg.jar
set dir=%~dp0

echo Starting MyProg
set pid=notfound

for /F "usebackq tokens=1,2 delims=;=%tab% " %%i in (
    `wmic process call create "%cmd%"^, "%dir%"`
) do (
    if %%j gtr 0 (
        set pid=%%j
    )
)

echo %pid% > MyProg.pid

Most often you do know what task you start - in this case, which page iexplorer shall show.

So how about

taskkill /FI "Windowtitle eq *yourpagetitle*"

It will kill all instances of something showing your page title, but with a specific title most often there should be exactly one.

Tom

Ummm, TaskList & TaskKill?!

For some reason your approach of getting process id did not work for me, but since I m expert in batches, I ve coded my own approach, attaching here:

@echo off

call:AsyncCmd
rem call:AsyncCmd "echo hello world"
rem call:AsyncCmd "call build.bat"
exit /b

rem ------------------------------------------------------------------------------------------
rem Starts asynchronous command execution 
rem %1 is command, if empty - only aborts existing build.
rem ------------------------------------------------------------------------------------------
:AsyncCmd
if exist %~dp0SetupBuild_Completed.txt (
    del /f %~dp0SetupBuild_Pid.txt >nul 2>&1
    del /f %~dp0SetupBuild_Completed.txt >nul 2>&1
)

if not exist %~dp0SetupBuild_Pid.txt goto lStartProc
    rem --------------------------------------------------
    rem Abort build process
    rem --------------------------------------------------
    set /p pid=<%~dp0SetupBuild_Pid.txt
    echo Cancelling setup build process, process id %pid%
    pskill -t %pid%
    del /f %~dp0SetupBuild_Pid.txt >nul 2>&1

:lStartProc
if "%~1" == "" exit /b 0

rem --------------------------------------------------
rem Starts asyncronous build process
rem --------------------------------------------------
set dir=%~dp0
set dir=%dir:~0,-1%
for /f "tokens=2 delims==; " %%a in ( wmic process call create "cmd /c mincon.exe && %~1 && echo 1>%~dp0SetupBuild_Completed.txt"^, "%dir%" ^| findstr /r "ProcessId" ) do set pid=%%a
echo Setup build started, process id: %pid%
echo %pid%>%~dp0SetupBuild_Pid.txt
exit /b 0

PowerShell can be used for this:

powershell -executionPolicy bypass -command "& {$process = start-process $args[0] -passthru -argumentlist $args[1..($args.length-1)]; exit $process.id}" notepad test.txt

echo Process ID of new process: %errorlevel%

I think you can t do that with simple command line utilities, as IE actually spawns child processes for each tab, i.e. if IE is not yet running you would get one parent IE process and a child process for the tab, and if IE is already running you would simply get a single child process.

It will be even quite tricky when you write your own tool to kill IE because when you kill a child (tab) process, IE will automatically recover this tab.

See also this related question: How to obtain process of newly created IE8 window? (though there is no good answer there).