Please understand that Rav Hool is literally ''going to war'' on your behalf to destroy your ayin horah. Rav Hool feels that the Siyyatah Dishmayah (Heavenly help) he has in succeeding, is due to the kaboloh of a mitzvah the person undertakes.
The person who has the procedure done for them (or the person ordering it on their behalf) should undertake to strengthen themselves in a certain mitzvah of their choice. They do not need to tell Rav Hool what their kaboloh is.
It is NOT a verbal promise or 'neder' and you do NOT have to worry if you miss doing it a few times, we just need 100% intention for you to do it when Rav Hool does the procedure, (that is why we insist on only a very small undertaking):
It cannot be stressed enough that this kaboloh HAS TO BE very, very SMALL! This is because the kaboloh has to be 100% genuine! For example- Rav Hool told a non-religious couple "You cannot put on two shoes at once in the morning. You have to put on one shoe before the other. There is a halochoh that you should put on your right shoe before your left. I ask you to -from now on- start putting on the right shoe first, and in the merit of this mitzvah we will have Siyyatah Dishmayah (Heavenly help) in destroying your ayin horah.''
Other examples people have undertaken: Kavonoh during asher yotzar at least once a day. Kavonoh during lehisatef batzitzis. Saying 'Mizmor leDavid Hashem roey' during a meal (takes 20 seconds- also segulah for parnossoh!). Kavonoh on brochoh lehaniach teffillin. Never missing modeh ani in the morning.
Maybe other people who do this procedure do not have this requirement, however Rav Hool only agrees to do the procedure if a kaboloh is made.