Graphics Slider - Set Value

Hi all, I have currently developed a graphic slider bar (set to "Grades" display) but having problems being able to set it's value manually to a value of 1 using javascript. Firstly I tried using the this.setChoiceAnswerValue(1,1) . But this doesn't set the value. I can get the value easily but trying to set it is proving difficult The above method definitely works using the non graphic slider bar as well as other question types but doesn't seem to work using the graphics slider bar. I played around with the Qualtrics API a lot to try and do this with no such luck! Also unlike with the standard slider bar, when I view it's rendered html I can't see anywhere where it's storing the selected value. If I can somehow find the html element that might be storing it, I could then try setting it's value directly instead of using the Qualtrics API.
Any help would be greatly appreciated!