Search Value of column E if exist return value of column B put result in column P

Dear jarj1106 , thanks for your attention, but i still have some problem :
1-Code just work with Grade F in cell L1 , but other Grade ( A,B,C,D,E, ext in column S ) not working , i mean column S ( from S2:S1000 as example is the range of Grade ) and the column T ( from T2:T1000 as example ) is the Value of Letter adjacent in column S.
2- if i press the command button Grade many times i want the result one time , if i Re-press the command button again i want the result start from cell P2 , and cell S2 ( over the old result first press ) as new result , and not double the result below first result . i mean when i press the command button many times the code should get the result as first press and result should always begin from 2nd row ( P2 , and S2 ) .
see new attached file

Thanks a lot jarj1106