=SI(SOMMEPROD(($A5=0+GAUCHE('2'!$A$2:$A$854;2))*(B$4>='2'!$B$2:$B$854)*('2'!$B$2:$B$854>A$4));
SOMMEPROD(($A5=0+GAUCHE('2'!$A$2:$A$854;2))*(B$4>='2'!$B$2:$B$854)*('2'!$B$2:$B$854>A$4)*'2'!$C$2:$C$854)/
SOMMEPROD(($A5=0+GAUCHE('2'!$A$2:$A$854;2))*(B$4>='2'!$B$2:$B$854)*('2'!$B$2:$B$854>A$4));"")