There are 2 kinds of subVIs - one is the VI that performs a specific function and outputs the results and the other is called once and runs continuously. If you want the top VI loop to continue running while the subVI runs, you need to place it in another loop or run it dynamically using the Run VI method and set Wait Until Done to F. If you do run the subVI in another loop, you can open its FP by double clicking its icon in the BD (while the VI is running), or by setting its FP.Open property to T. You can close it by setting the property to T. Search the example finder and this site for property nodes to see how to work with them.
If this didn't help, I suggest you save your VIs as an LLB and post them with some more details of what you want to do.
___________________
Try to take over the world!