I have recently been setting dynamic blocks to replace our existing standard blocks.
Basically, we want to have a dynamic block that can be stretched between two given points and then possibly use an array to automatically divide the distance between the two points equally and will not expant the centres greater than 1300mm.
i.e. overall length of run = 5000mm max centres = 1000mm = 5 divisions
see attached drawing, note that this isnt working how we want it too as the space between the posts is set to 1000mm, we need this to divide equally over the given length.
Can't be done. Arrays are limited to a specific distance just as you would (most) any Array.
That being said the new Array Command will let you add or subtract entities from a given distance and then will respace the remaining entities within that space so what you seek can be done outside of Dynamic Properties.
You would need to make sure that spacing did not fall outside of your parameters thru the Properties panel.
This may be able to be set up thru additional programming.
BTW - If you wish for all the ballusters to increase in height include the Array balluster in the vertical Stretch Action (Stretch2) as well as the rail.