Automatic limitation of the number of Characters in cells

Good day everyone,

I have a worksheet that I currently working on that where I have to limit the characters in some cells to 40 characters I know I could use the data validation but the point is that I need it to delete the excess over the 40 characters and not like the data validation to delete everything once it doesn't meet the criteria

the idea of the macro
my vision is that I need it to be activated once the cell is pasted in send a message box that "the Characters have been reset to 40"

I have tried multiple codes with almost none of them working the one that I got so close to went into an endless loop of copying and pasting. since I created a hidden column ( lets call it E) where I used a formula to limit the letters to 40 and the idea of the code was to check if there is a value in that cell in column E and then copy and special paste values into the other column ( lets call it B) making me un able to use the sheet anymore.

now I ran out of ideas on how to solve this issue

please tell me if there is anything that is not clear so I can rephrase it since even I find it complicated to describe something I don't fully understand

your help is much appreciated.

Kind regards,
George.m