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

Thanks a lot jraj1106 for your help, this Macro what i need , but i still have a problem that is
1-if i press two times or three times on command button, the Macro give me the result two times and three times below other, what i need , when i press more than one time on command button the result one time begin as new after each press and not conteniously.
2- i have in Column S Grade Letters ( A,B,C,D,E,F, ext .. ) and in Column T the value of Each Letters ( 95,90,85,80,50,40 and Ext ... ) i need from you a Code , if i type a letter F in cell L1, the Code should search the column E for Value of Grade F ie ( Less or equal 40 ), and put the result in column Q .
see attched file
many thanks for your help Mr. Jarj1006