Custom functions in mac excel 2008

I use to be able to access custom functions that I wrote and imbedded in the local module of my spread sheet. These functions were written in VBA.<br>
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Is there any way now to simulate this with apple scripts.<br>
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For example:<br>
My function call in the Excel spread sheet side was NAV(range) and in the local module was>><br>
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Function NAV(myRange)<br>
    NAV = 1<br>
    For Each i In myRange<br>
        NAV = (i + 1) * NAV<br>
    Next i<br>
    NAV = NAV - 1<br>
End Function<br>
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I am hoping for a help because otherwise this will be then end of excel for me.