Returns the width, in character units, of the string using the specified font. If no font is specified, the method calculates the width of the string using the default font.
A character-string expression whose width you want to determine.
font
An integer expression that specifies an entry within the font table.
If you pass the Unknown value (?) to this method, the AVM uses the system default font. When a field-level widget inherits its font from the parent frame, the AVM returns the Unknown value (?) for the font and you must use the font of the parent frame.