I have setup the reference to ATPVBAEN.XLS in my project, the Add-In is
installed in Excel, I also found the function in the Object Browser under
atpvbaen.xls.VBA Functions and Subs.

Nevertheless I can't make my code work, getting the "Object doesn't support
this property or method" prompt, when writen like this:

rngXIrrCalc = Application.WorksheetFunction.XIrr(rng1, rng2)

I would greatly appreciate if someone can help me with this.

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Any help will be appreciated.

Regards,

CyberBuzzard