I need to go month to month with a value at the beginning of the month, a
cash flow at some point the middle of the month, and a value at the end of
the month. I'm trying to get the ROR for that month.

For example:
$67,626.52 2/29/2008 known starting value
-$3,921.48 3/6/2008 cash flow
$72,906.91 3/31/2008 known value at end of month

If I set this up in XIRR, I get 0.000..

If I build out using a row for each day of the month "from known starting
value" through "known value at end of month" (thus including the cash flow as
a positive number since I'm putting monto into the account) and use Goal Seek
to find an answer, I get 0.0613%

What is the right answer and how do I get there from here?