excel training program - IF Function range

I'm attempting to check five cells on another worksheet and return a blank response if any of the five cells are blank, otherwise, I want the SUM of those five cells returned.

I have successfuly been able to create an equation for FOUR or less cells, but when I attempt five, I am either told that I have made too many arguments or it simply will not work correctly.

Here is a sample of what I am trying to accomplish, but this returns the SUM of those fields with an entry, it should return a blank response if any of the cells are blank (which is the case):

=IF(OR('Out by Source'!F14,'Out by Source'!F27,'Out by Source'!F47:F49)="","",SUM('Out by Source'!F14,'Out by Source'!F27,'Out by Source'!F47:F49))

Here is a working example of only four cells, I had to use a different approach entirely and had to leave off one of the cells in the logical test:

=IF(OR('Out by Source'!F14="",'Out by Source'!F27="",'Out by Source'!F47="",'Out by Source'!F48=""),"",SUM('Out by Source'!F14,'Out by Source'!F27,'Out by Source'!F47:F49))

As you can see, I had to leave the F49 out of the Logical Test because when I do not use a range (ie F47:F49) it will work, but only allows four entries, when I try five entries it returns the too many arguments error box.

There has to be a more streamlined equation, please help! Sorry for rambling, I hope it makes sense. ;)