averaging varying column entries

thanks donkeyote

nearly there - only problem is if all 4 values 0

(actually displays an X something I did on the original weekly sheet - =IF(ISERROR(SUM(O14/(M14/4.546))),"X",SUM(O14/(M14/4.456))),

EDIT:

have changed above to give "0" values - =IF(ISERROR(SUM(O14/(M14/4.546))),"X",SUM(O14/(M14/4.456))),

calculation returns #DIV/0! value which messes up formulae for calculating largest and smallest - can I get it to display "0"

much appreciated