No you may not. Different class of medicine altogether. Betimol does not cause eyelash growth, do not use glaucoma meds interchangiably. Both lower the intraocular pressure, only Latisse (Bimatoprost 0.03%) causes lash growth
Betimol is not a substitute for Latisse. Timolol (Betimol) belongs to a completely different class of drugs -- beta blockers. Beta blockers have a much more frequent incidence of systemic side effects, like exercise intolerance, erectile dysfunction, and heart rate changes. Be very careful using prescription medications without doctor supervision!
Betimol is timolol which is a "beta blocker" medication and has no relationship to Latisse (bimatoprost). It can therefore not be used in place of Latisse and has not been proven to stimulate the growth of eyelashes.