No. Custom functions are executed one at a time.
The PLC evaluates your ladder logic program one rung at a time from the top to bottom of your program.
If a custom function is invoked during the evaluation of a ladder logic rung, then the PLC will wait until the custom function completes before continuing to the next rung of the program.
If your custom function "waits" for some event, then execution of the PLC will wait, also.
You should rethink your approach. If the "enter" key is a discrete input to the PLC, invoke a custom function when this key is pressed:
Enter EnterPressed
----||-----------------------{dCusF}
This is only part of what you need to do, but it should point you in the right direction.
There are sample programs written for TriLogi's HMI interface. Look for "HMIxxtoyy.PC6". The HMI hardware looks like a bunch of separate input switches to the PLC. They demonstrate a method to handle input without hanging up the execution of the PLC program. Look for files with names: "HMIxxtoyy.PC6".
Good luck,
Gary D.