Clear Field Value in VBS keeps clearing the field on Employment processes

Summary:

I'm creating business rules for Add Assignment and Global Transfer and i want fields (like - Person Type, Assignment Status, Assignment Category, Working hours ) - all to be cleared when assignment section loads. We've had many problems where these fields default and the HR team forget to check them.

Unfortunately, the clearing function is working too well - if you select an option and then move to the next field the Clear field happens again and you have to reselect - this can happen more than once till the information 'sticks'

I can't work out a way to set a condition so that it only clears on page load. I'm only working in express mode - do not have access to more advanced VBS