How to increment counter variable in "DOS" batch file

I try to create a batch file to run under Windos XP in a command window (or just double clicking the BAT file).

The intention is to take all files with a given extension, concatenate them and add some extra information "between the files". To do this, I need to add a counter value like 1 for the first file, 2 for the second and so on. I have managed to solve all other problems to output what I need but the counter variable is not updated as long as I'm inside the FOR loop. See the attached code example. Put it in a BAT file and run it to see the problem. The last echo after the FOR loop gives the correct value.

Any hints are much appreciated.

@echo off
 
set /A Counter=1
 
echo Initial value of Counter: %Counter%
echo.
 
for %%f in (*.*) do (
	echo File found: %%f
	echo Counter Before increment: %Counter%
	set /A Counter+=1
	echo Counter After Increment: %Counter%
	echo.
)
 
echo Counter after for loop: %Counter%

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