I have a simple "on user input" invoked function to make some text conform to a standard.

input.RMC = thisapp.inventory.RMC_CHECK(input.RMC);

It works, but the "on user input" keeps running forever (little spinning arrow next to input field).

How can I specify this function to only run when a human changes the input field, and not when the function itself acts on the string in the field?