How do I upgrade just mine return and not my husband's. His is only a t4 so I don't want to spend 100 to do his

If you want to prepare your return together with your spouse, then you will both will be using the same version of the program, and you will both be charged the same price. You can only prepare your returns in different products if you prepare your returns separately. In previous years there was a discount for the spouse, but unfortunately, this is no longer the case.