find string from multiple files and replace it without creating new file

I want to find string e.g. "date" from my files of a folder which contains multiple ".c" and ".h" files in it and replace it with "date 24-April-2018" using batch file. what should do? Please see below code. I want to do the same but not for one file Input.txt , I want to do for multiple files with extensions of a folder

@echo off
setlocal enableextensions disabledelayedexpansion
set "search=@date"
set "replace=@date 24-apr-2018"
set "textFile=Input.txt"
for /f "delims=" %%i in ('type "%textFile%" ^& break ^> "%textFile%" ') do ( set "line=%%i" setlocal enabledelayedexpansion >>"%textFile%" echo(!line:%search%=%replace%! endlocal
)

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