Try this out for yourself in a new worksheet:

Here is the required information:

A3: Type some text
A4-A14: 2101
F4-F14: =date(2005,8,5)
I4-I14: 23974
K4-K14: 42
N3: Type some text
N4 [drag to N14]: =IF(A4=A3,N3+330,IF(M4="",(F4+330),((M4+330))))
O4 [drag to )14]:
=IF(ISERROR(IF(A4=A3,(O3+((N4-N3)*L4)),IF(((N4-TODAY())*L4)<0,"OVERDUE",((N4-TODAY())*L4)+I4))),((N4-N3)*L4),IF(A5=A4,(O4+((N5-N4)*L5)),IF(((N5-TODAY())*L5)<0,"OVERDUE",((N5-TODAY())*L5)+I5)))

Put the formula in O4 and drag down to O14 and then calculate the
workbook (F9). Alternately, keep pressing shift-F9 to watch the results
roll upward for infinity.

Strange strange strange...

Whats causing this? Is it documented? Can it be used somehow?

-Sean