Slider configuration to avoid skipped entries with 99 (case 8747)

Could you please help me to find a solution to a problem with slider 'continuum' and blank data entries containing 99.
Our questionnaire uses the skip function based on the persons previous response. In this case the DATA is populated with 99. It so happens that we wish our subjects to respond with the slider ranging from 0-100 to represent the percentage they choose to a previous item instruction. If they move the slider to 99 it is difficult to differentiate between skipped data and real 99 responses. At the moment we have to reference the question order to see which data they actually responded to.

I can think of two simple solutions:
1. Change the default for skipped data from '99' to '999'. Is this possible?
2. I changed the scale to min100 and max200 and in range.js set this._maximum = 200 . Now I need to somehow change the right number display on the slider to -100 so the subject sees a scale between 0-100 again. How can I accomplish this?

You can change the missing data value to whatever you want quite easily. As it says in the Data > Data FAQ section of the MediaLab manual:

Can I change the value used for missing data?
By default, 99 is used as the value for missing data. Because most item types are either open ended or limited to a numeric value of 12, 99 is usually safe. However, if you suspect 99 might be a dangerous value for your particular study you can choose an alternate value. Simply create a text (.txt) file in your experiment folder and name it "missing.txt" and on the first line of that file, enter the alternate value. It must be numeric.