Page 66 - Microsoft Office Excel 2003 Programming Inside Out

Microsoft Office Excel 2003 Programming Inside Out

the macros in the workbook you’re trying to open, the security routine will either require
your permission to trust the source that signed the macro or will disable macros entirely.
You can add a trusted source to Excel by opening the file that contains the digitally signed
macros from the developer that you want to add to the list. A Security Warning box will
appear, indicating the publisher is not on the trusted list. To add the publisher to the list of
trusted sources, select the Always Trust Macros from this Publisher check box and click
Enable Macros.

Note Your network administrator can prevent users from adding sources to the list of
trusted sources, so you might need to ask your administrator to add new developers to
the list.

There are a number of scenarios under which digital signatures and macros can interact with
Excel when the macro security level is set to High; Table 3-2 summarizes those situations and
the effect of the High security setting.
Table 3-3. How Excel Reacts to Various Digital Signature Scenarios When
Macro Security Is Set to High
Circumstance Reaction
Chapter 3
The macro does not have a digital Excel disables macros and opens the work-
signature. book.
The macro has a valid signature from Excel enables macros and opens the workbook.
a trusted source.
The macro has a valid signature from Excel displays information about the certificate
an unknown source. used to sign the macro and, if not disabled by a
network administrator, asks if you want to trust
the source and the certification authority.
The macro has an invalid signature, Excel disables macros and warns you there
indicating the file might have been might be a virus.
corrupted by a virus.
The signature can’t be verified Excel disables macros and indicates it was
because the public key is missing or unable to verify the signature.
can’t be found on a key server.
The macro was signed with a certifi- Excel disables macros and indicates the certifi­
cate that has either expired or has cate is invalid.
been revoked.

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Part 2: Visual Basic for Applications