Recategorizing expenses

Hello all. I have a question on how to recategorize expenses. When I withdraw cash from my bank account, I put that amount in a category called Cash expenses because I don't know what I will be spending it on. Later, when I spend some cash to say, pay for a meal at a restaurant, I would like to move that amount from Cash expenses to a category called Dining Out expense. How would I do that?
Thanks.