So your problem is really about fixing the #Div/0 error? See the Excel Help topic 'Correct a #DIV/0! error'. An extract from thsi topic states...
"Prevent the error value from displaying, using the IF worksheet function. For example, if the formula that creates the error is =A5/B5, use =IF(B5=0,"",A5/B5) instead. The two quotation marks represent an empty text string. "
Ideally you should correct this in all your source sheets (see why having 72 sheets may not be a good idea) or alternatively use an if statement looking for ISERROR and put in 0. If there is an error, this will affect your efforts in trying to sum and average results.
eg for cell B2 in your example ...
=If(Iserror('[Machines by Number.xls]1'!$M$9),0,'[Machines by Number.xls]1'!$M$9)