Maybe use those exact words? To my mind they are clearer and more precise--and the second half is more personal/intimate.

You could also ask him to do a "test run". In other words, ask him to try it out, explain how to do it, and then let him see for himself how much it can help you.

And when (in the test run) he says "I want to fix it for you,", something like that, you can gently remind him that the test run is on at the moment...