Unfortunately, you can't dynamically control a cluster's size.
If you're only concerned about display, you can use the property NumRows to control the number of rows displayed. To do this, you need to create a property node. Right click on the control or the terminal and select Create>>Property Node. Then, find the property and wire the proper number in.
If this didn't help, please write more about what you're trying to accomplish.
Also, your post came out twice. You should try to avoid that.
___________________
Try to take over the world!