This function is used to safely convert a hexadecimal value into a long integer. VBSCRIPT has no way to do this safely.
An example of what you might try is the expression "clng(&H8000)", this will fail as the hex literal is first converted to a short integer and then converted to a long one.
The function takes these parameters:
The value can (but doesn't have to) begin with either "&H" or "0x" (in any case).