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.

Clarification and Follow-Up,
----------------------------------
When using code such as that given below, the following two lines are
output in the
Immediate window as soon as .Formula is executed.

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

With rngXIRR
.Formula = sXIRR ' SXIRR has a valid XIRR formula
.NumberFormat = "0.000%"
.Name = "'" & sThisSheet & "'!" & "WattEver"
End With

Using Google, I found postings indicating that such statements are produced
by Debug.Print in the Analysis ToolPak
If true, all I can say is @$@$%@!!@#.

The suggested solution was to crack the password for the .XLA and modify the
code.
If the password for an XLA is as easy to crack as that of an .XLS, this
would be doable.
MSFT should fix this themselves if the onlty problem is the stupidity of the
developers leaving in such code.
Guess they never heard of comments or conditional compile.