The width of a string in pixels

There was command in Blitz3d, called StringWidth()

This will return the size, in pixels, the width of the indicated string. This is useful for determining screen layout, scrolling of text, and more. This is calculated based on the size of the currently loaded font.

I need this function but I think there isint one in BlitzMax. And I have no idea how to write one.

I need this to center a text