excel - XIRR function with extremely low ending value

Question

I have a macro that calculates XIRR; used to tell me the rate of return on an investment.

The relevant code is:

Dim CFArray() As Variant
CFArray = Range("Q22:Q24").Value

Dim DateArray() As Variant
DateArray = Range("L22:L24").Value

ROR = WorksheetFunction.Xirr(CFArray, DateArray, 0.1)

The code works most of the time.

But when the ending value is extremely low, say zero, or a penny, I get

"Run time error '1004': Unable to get the XIRR property of the worksheet function class".

Here is my data:

Row  Col L         Col Q
22   6/30/2009     999.07
23   5/1/2010         .01

When I change the final value (cell Q23) to 5.01 or 4.01, I get an answer. 3.01 returns the same error as above.

Using the data in a plain old Excel formula (in a cell) yields a correct answer... something like -99.99%.

Some series will have multiple payments and withdrawals, so IRR is not an option. I believe I can write code to literally write the Excel function in the cell, but it seems like VBA should be able to accommodate this essential financial function.

Thanks for any insights.