Does Excel VBA have a built-in function to test if a
string variable contains ONLY whitespace characters?

For my purposes, a whitespace character can be any one of
the following: space, tab, or enter (carriage return).

I know regular expressions solves this easily, but I do
NOT want to use regular expressions for this. I'm just curious
if Excel has a built-in function to test if a string contains
1 or more of the above whitespace characters.

Thank you.

Robert