Can you detect in a VB script how many characters are in a string and based on that number decide what value to return to a field?

You can do this in a VB script using the  len() function.  Here is an example:
 
ifs(len(FieldA)>10, "Greater Than 10", "Not Greater Than 10")
 
This means that if FieldA contains more than ten characters, then the field containing the field script should be populated with the text "Greater Than 10" (without the quotes).  If FieldA contains less than ten characters, then the field containing the field script should be populated with the text "Not Greater than 10" (without the quotes).
 
 
Please note that leading and trailing spaces in your field will be included in the character count unless you use trim() inside the len().