Press button only once to repeatative work

Question

I am new to C# ( i really mean a beginner). I want to create a button (let say button A). Once i clicked this button, the curson will change to let say a hand icon. After that i can click on anywhere in the form and a certain function will be run. I need to always use this function but i just want to click on the function button A only once. If i want to disable this function, i will like to press other function button and the function of button A will be disable. Can it be done? Thanks.