"Rick Rothstein \(MVP - VB\)" wrote...
....
Another possibility, with special note to Harlan's remark in his
reply to my other post in this sub-thread, namely,

"Event handlers only work when macros are enabled,
and it's simple for users to disable macros"

is to create your own format checker via a macro. Here is a
function macro that should be usable which will expose VBA's Like
operator for use in a worksheet. . . .
....

udfs are also disabled when macros are disabled.

udfs are also slow due to the Excel/VBA interface. If you're going to
incur udf overhead, better to go for something more useful than VBA's
Like operator, e.g., the VBScript RegExp (regular expression) object
for which there are many examples in the Excel newsgroups.