Chances are that really, it is not the accent grave character itself, but a character that is a combination of the letter "e" and the acent grave character, meaning, one character é or è depending on what you actually have. So, that means it is either ascii # 232 or 233.
Try this, select your range of interest, press Ctrl+H, and activate the Replace tab.
In the Find What field, press the Alt key and enter 0233 on your keyboard to simulate that character.
In the Replace with field, enter the letter e
Click the Replace All button amd see if that does it. If not, repeat the above steps but this time, for Find what, enter Alt+0232 and replace with e.