dimension to intermediate posts in a length of rail

[madcowscarnival]

I read a similar thread, but it was in regards to dimension behavior at each end of a rail "wall".  Is there a way/setting to allow a dimension to locate the center of a "post-to-beam" in an automatic railing on a porch.  i.e. a 54' long porch, automatic 5x5 posts at 8' spacing result in posts at ~6'-9"?  The 54' number worked out well, but I would like to show post to post dimensions when it divides out to something like 7' 4-5/8" (made up number).  I know I can create a CAD detail and set up dims with that, just curious if there is a non-manual option available.