How to manipulate a string and variable inside same loop

1 Need help to shorten the code

2.(If posible) about case sensitive when mapping

Sample.Bat:

@echo off & setlocal EnableDelayedExpansion
set "Data=HELLO"


:Encrypt/Decrypt_Rot13

set Encrypted_Data=!Data!
set Encrypted_Data=!Encrypted_Data:A=A#!
set Encrypted_Data=!Encrypted_Data:B=B#!
set Encrypted_Data=!Encrypted_Data:C=C#!
set Encrypted_Data=!Encrypted_Data:D=D#!
set Encrypted_Data=!Encrypted_Data:E=E#!
set Encrypted_Data=!Encrypted_Data:F=F#!
set Encrypted_Data=!Encrypted_Data:G=G#!
set Encrypted_Data=!Encrypted_Data:H=H#!
set Encrypted_Data=!Encrypted_Data:I=I#!
set Encrypted_Data=!Encrypted_Data:J=J#!
set Encrypted_Data=!Encrypted_Data:K=K#!
set Encrypted_Data=!Encrypted_Data:L=L#!
set Encrypted_Data=!Encrypted_Data:M=M#!
set Encrypted_Data=!Encrypted_Data:N=N#!
set Encrypted_Data=!Encrypted_Data:O=O#!
set Encrypted_Data=!Encrypted_Data:P=P#!
set Encrypted_Data=!Encrypted_Data:Q=Q#!
set Encrypted_Data=!Encrypted_Data:R=R#!
set Encrypted_Data=!Encrypted_Data:S=S#!
set Encrypted_Data=!Encrypted_Data:T=T#!
set Encrypted_Data=!Encrypted_Data:U=U#!
set Encrypted_Data=!Encrypted_Data:V=V#!
set Encrypted_Data=!Encrypted_Data:W=W#!
set Encrypted_Data=!Encrypted_Data:X=X#!
set Encrypted_Data=!Encrypted_Data:Y=Y#!
set Encrypted_Data=!Encrypted_Data:Z=Z#!

set Encrypted_Data=!Encrypted_Data:A#=N!
set Encrypted_Data=!Encrypted_Data:B#=O!
set Encrypted_Data=!Encrypted_Data:C#=P!
set Encrypted_Data=!Encrypted_Data:D#=Q!
set Encrypted_Data=!Encrypted_Data:E#=R!
set Encrypted_Data=!Encrypted_Data:F#=S!
set Encrypted_Data=!Encrypted_Data:G#=T!
set Encrypted_Data=!Encrypted_Data:H#=U!
set Encrypted_Data=!Encrypted_Data:I#=V!
set Encrypted_Data=!Encrypted_Data:J#=W!
set Encrypted_Data=!Encrypted_Data:K#=X!
set Encrypted_Data=!Encrypted_Data:L#=Y!
set Encrypted_Data=!Encrypted_Data:M#=Z!
set Encrypted_Data=!Encrypted_Data:N#=A!
set Encrypted_Data=!Encrypted_Data:O#=B!
set Encrypted_Data=!Encrypted_Data:P#=C!
set Encrypted_Data=!Encrypted_Data:Q#=D!
set Encrypted_Data=!Encrypted_Data:R#=E!
set Encrypted_Data=!Encrypted_Data:S#=F!
set Encrypted_Data=!Encrypted_Data:T#=G!
set Encrypted_Data=!Encrypted_Data:U#=H!
set Encrypted_Data=!Encrypted_Data:V#=I!
set Encrypted_Data=!Encrypted_Data:W#=J!
set Encrypted_Data=!Encrypted_Data:X#=K!
set Encrypted_Data=!Encrypted_Data:Y#=L!
set Encrypted_Data=!Encrypted_Data:Z#=M!

echo. 
echo. Original Data:%data% 
echo. 
echo. Encrypted/Decrypted Data:%Encrypted_Data%
echo. 
pause

As you can see, i use mapping method and It worked perfectly (Input=HELLO,Output=URYYB),But i realy it tiring to modify it one by one if Needed or to make it as micro.

But when i trying to Shorten the code by using Loop and using same method .

Sample.Bat:

@echo off & setlocal EnableDelayedExpansion

set "Data=HELLO"

set "Process=Rot13"

set "Rot13_input= ABCDEFGHIJKLMNOPQRSTUVWXYZ"
set "Rot13_output= NOPQRSTUVWXYZABCDEFGHIJKLM"

::set "xxxxxx_input= xxxxxxxxxxxxxxxxxxx"
::set "xxxxxx_output= xxxxxxxxxxxxxxxxxxx"

if %Process% equ Rot13 set "Maxdigit=27"

for /l %%n in (1,1,%Maxdigit%) do ^
set "%Process%_input_%%n=!Rot13_input:~%%n,1!" & ^
set "%Process%_output_%%n=!Rot13_output:~%%n,1!"

::set Rot13_input_
::set Rot13_output_

set Encrypted_Data=!Data!

:: STUCK BELOW ::

for /l %%n in (1,1,%Maxdigit%) do ^
set Encrypted_Data=!Encrypted_Data:%Rot13_input_%%n%=%Rot13_input_%%n%#!

echo %Encrypted_Data%

:: STUCK ABOVE ::

pause

echo. 
echo. Original Data:%data% 
echo. 
echo. Encrypted/Decrypted Data:%Encrypted_Data%
echo. 
pause

I am stuck(error output) at second LOOP,Can anyone fix this or Maybe another methods it can be done?