VBS use the Len function prompt type mismatch

Today wrote to extract the code length of the string section, as follows:

    Dim strF,freq
    Dim len
   
    freq = 200 

    strF  = Cstr(freq)

    len = Len(strF) 'error

Program always len = Len (strF) This sentence prompted len type mismatch here; originally thought len ​​is variable, Len is a function; toss to think through a variety of VBS should be case-insensitive;

VBS will also be used as a function len. So will the error. The variable name num len changed no problem.

        Although the problem is not still record, remind yourself!