On a open and called sub vi, how can I change the value of a wired but not connected input control? Every time the vi is called, the modified value is replaced with the default value.
I'm not exactly sure what you are meaning. If you are wanting to change the default value permanently you can do this under the Operate menu by choosing the Make Current Values Default selection item. If you want to make the value of the control at exit the startup value the next time then you can do this same operation programmatically using an invoke node. Otherwise, you need to pass the value to the sub-vi.
I'm not clear either on what you're attempting to do. If you want the user to be able to change a value of a subVI, your subVI should have a while loop that waits for a value to be entered and then the user would click on an "OK" button.
