$width
From Scriptwiki
Returns width of text in pixels for the specified font.
$width(text,font,size,B,C)
If B is non-zero, the font is bold, if C is non-zero, control codes are processed. Both B and C are optional.
Note: If you use a negative number for the font size, it will match the size of fonts in the font dialog.
Example
$width(Lorem ispum,Arial,12)
Returns 74.