Hi Nick,

I have created a custom cert in Office 2003 and attached it to VBA code.

On the computer (Office 2003) which create this cert, when excel
security is set to high, I was able to check "Always trust macros from
this published" and thus enable the macro.

Then I copy the same file to another computer, the security is also set
the high, but this time the "Always trust macros from this published" is
not checked. (grey out). How to check this box?

In general, certificates created using selfcert are not trustable on other
machines. If this is only one or two machines, you might be able to export
the selfcert certificate using Start Settings Control Panel Internet
Options Content Certificates and import it on the other machine, but
I've never tried it.

If you want to have a fully-trustable certificate, you'll need to buy one,
eg from www.thawte.com

Regards

Stephen Bullen
Microsoft MVP - Excel
www.BMSLtd.ie