Input Value Dependencies

I currently have a slider as shown in the image below.

If the user adjusts the Drawdown value the Annuity value is affected also and vice versa. This sounds simple, however, if a user wants to increase say the Annuity amount via the slider, they tend to drag the pointer towards Annuity, which actually increases the Drawdown value and reduces the Annuity value.

Originally, the slider contained two colours which helped a little but due to the constraints of our system the colours can not be added.

Can someone please advise on how this should be done.

Any suggestions will be greatly appreciated.