This is the formula I'm working with:

=OFFSET(INDIRECT("Canadianl!A"&MATCH($O$1,Canadian !$A:$A,0)),7,3)+(OFFSET(INDIRECT("US!A"&MATCH($O$1 ,US!$A:$A,0)),7,3)*$O$2)

In the worksheet called "Canadian" there must be an exact match or it should
return #N/A, but in the sheet called "US" there will not always be a match.

So what I need is: sum the values from "Canadian" and "US" if they both
match, but if there is no match in US return only the value from "Canadian".

Hope that makes sense!

Cathy