Hi Hollie,
Your problem would be asked otherwise: how do you withdraw the previous job title score value before adding the new one.
It really depends on how you have implemented your scoring.
If you only have 1 scoring field for both behavior and demographic or if you have implemented it the way it's done in Marketo's importable programs, you will have to create a series of smart campaign that test both new and previous value. E.g.:
- data value changes - job title - Previous value contains "VP"
- Choice: Job Title contains "Executive" -> +1
- Choice: Job Title contains "Manage" -> -5
- ...
- Data value changes - job title - Previous value is Executive
- Choice: Job Title contains VP -> -1
- Choice: Job Title contains "Manage" -> -6
- ...
- Data value changes - job title - Previous value is empty ->
- Choice: Job Title contains "Executive" -> +9
- Choice: Job Title contains "VP" -> +8
- ...
I you have to combine multiple titles, it wan become very cumbersome. Let's say you have N possible job titles, N+1 smart campaigns, and in each one, N+1 choices 
The alternative is to store the previous value in another fields. Then in your smart campaign, you will first decrease the score based on the previous value, then increase based on the new one, and finally copy the new value to the previous value field. Typically, in your case, the flow will be something such as
- change score.
- Choice: if previous value is VP -> -8
- Choice: if previous value is Executive -> -9
- ...
- Change score
- Choice: if job title is Executive -> +9
- Choice: if job title is VP -> +8
- ...
- Change data value - Attribute: Previous Value - New value: {{lead.Job Title}}
This method will break if you decide to change the scoring values.
I personally have stopped using this technique quite a while ago exactly for these reasons. I use a system by which the demo score is a separate field and is recomputed from 0 each time one of the criteria changes, making it much more accurate. The process is to use 1 unique smart campaign with multiple triggers. In the flow, you reset the demo score to 0, then add the exact number of points for each criteria.
-Greg