Glad that helped!
Defining your goal is the most difficult. The rest is relatively easy. Now that you have your goal, take time work on the selection criteria! The principle is to define a cohort that will maximize the effects.
I think the percentage of success will be reduced upon this measure.
Do you not have confidence in your claim that it will reduce the occurrence? Then choose something you have confidence in , e.g. Severity. You have to choose something you have confidence and are comfortable with.
If it cannot be defined as preventive treatment, can the occurrence be still used as a measure?
yes.
Are you a longtime XYSer?
how do you define long or short? I may be considered short time. about a year.