Custom Linestyle query

Hi all, I'm trying to create a custom linestyle but I'm not quite sure if the style I want to create is possible. What I am looking for is a style that resembles a regular toothed parapet. The style is to be used on some rectangles so the ends of the line need to be variable so that the size of each tooth remains the same and also so that the extents of the total number of teeth is centred along the length of the line. 

So far I have the single component as a point symbol but I'm not quite sure to get the style to centre and with the end segments variable at a maximum length of 37.5mm. I've gone through the help file but I can't find any examples (I'm sure older versions used to contain examples but I can't find any in V8iSS2 help)

Any suggestions welcome