Gary''s Student wrote...
I have not thoroughly tested this, but it seems to work:

Function numbit(r As Range)
....

Brute force would be bad enough, but your approach is even less
efficient. As a purely academic exercise, there's a MUCH BETTER way to
check strings in VBA for certain classes of characters, the Like
operator. For example,


Function foo(s As String) As Boolean
foo = (Not s Like "*[!-0-9]*")
End Function


FWIW, the udf above also works in Excel 97 and recent Mac versions
since it doesn't rely on the Replace function, which was added only to
Windows versions with VBA6 in Excel 2000.

However, no VBA is needed. The following returns TRUE if cell A1
contains nothing but hyphens and decimal numerals.

=ISNUMBER(-(SUBSTITUTE(A1,"-","")&".0"))

The &".0" bit is necessary because one of the OP's examples,
7-5-047-E14, is a valid number in scientific notation once the hyphens
are removed, but 75047E14.0 isn't valid.

Never use VBA when the same functionality can be achieved in relatively
short formulas involving no more than a few built-in function calls.
Excessive VBA use is a bad thing.