@echo off
set inifile=c:\windows\progman.ini
set groupfile=c:\myprog\myprog.grp
set n=1
if not exist %inifile% goto found

:chk
rem below code will check up to group number 20.
rem add more group number condition check code if needed.
>nul type %inifile% | find "Group%n%="
if errorlevel 1 goto found
if %n% == 20 goto toomany
if %n% == 19 set n=20
if %n% == 18 set n=19
if %n% == 17 set n=18
if %n% == 16 set n=17
if %n% == 15 set n=16
if %n% == 14 set n=15
if %n% == 13 set n=14
if %n% == 12 set n=13
if %n% == 11 set n=12
if %n% == 10 set n=11
if %n% == 9 set n=10
if %n% == 8 set n=9
if %n% == 7 set n=8
if %n% == 6 set n=7
if %n% == 5 set n=6
if %n% == 4 set n=5
if %n% == 3 set n=4
if %n% == 2 set n=3
if %n% == 1 set n=2
goto chk

:found
echo Next group number is %n%.
rem add [Groups] section if not yet exist
if not exist %inifile% goto addsection
>nul type %inifile% | find "[Groups]"
if not errorlevel 1 goto addgroup

:addsection
>>%inifile% echo [Groups]

:addgroup
>>%inifile% echo Group%n%=%groupfile%
goto end

:toomany
echo Can't find next available group number. Too many groups to check.
echo Please add more group number condition check code.

:end