What should a person do who vowed to donate five dinars for every glance at women, and a large sum of money has accumulated that he does not possess now, nor can he precisely calculate its value?

Looking at foreign women is forbidden and leads to great evils. Your statement, "If I look at women, I must give five dinars in charity," is an oath of obstinacy (Nathr Lajaj). If you violate what you have vowed, then you owe a single expiation for an oath (kaffarat yamin (definition)) according to most scholars, even if the action is repeated.