I never noticed this before, but when I assign an XIRR function using code
below:

rng.Formula= StringContainingXIRRformula

When running within Excel, it appears that Analysis Toolpak spits out, e.g.:

[GetMacroRegId] 'XIRR' <
[GetMacroRegId] 'XIRR' - '875692121'

Can that be disabled?
Does not appear if automating Excel from VB 6.

This is in Excel 2003, have not tried in other versions.