Searching Arrays on Excel for OS X

I'm working on making an existing macro-enabled spreadsheet functional on Excel for Mac 2011.

I have a function (Source) that searches arrays for a specified value:

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It works perfectly in Excel 2013, but on Excel for Mac 2011, I receive the error:
Runtime error '9': Subscript out of range

I broke it apart and found that the UBound call is what's causing the error.

I'd like to change as little as possible for maintainability. How can I fix this error for the Mac version?

Thanks in advance for any replies!

Solution: See StackOverflow