What accent over the e creates the ee sound?

If you are asking about diacritical marks used to gshow pronunciation in a traditional dictionary of English--and if you mean the vowel sound of "meet" as opposed to "met"--the the sound in "meet" is called a long "e" and is shown with a macron, or straight bar above the letter. The short "e" of "met" wild be shown with a symbol similar to a parenthesis ")" on its side, looking something like a smiling face.

HOWEVER, some modern dictionaries, even of English Words for use by speakers of English (and also most bilingual dictionaries) now use International Phonetic Alphabet, and the vowel of English "meet" would be shown with the letter "i" while that of "met" would look sometiong like a mirror image of "3".