I have a planner page that has 3 tables across the top, showing the days of the week (Sun-Fri), the Month Names (JAN-DEC), and the 31 dates (01,31). On a layer behind, there are colored oval objects circling each table entry, all set to 100% transparent. Based on a date I enter, I'd like to be able to change the transparency for specific ovals to less than fully transparent, so the correct values for the date appear to be circled. Any pointers on how I might be able to do this?
Rather than ovals behind the date text frames/table, you could leverage Paragraph Shading and Find/Replace on various paragraph styles to get the effect you want, applying the right paragraph shading style to the date text you want. Otherwise, like with most things, it's probably possible with script, but would require looking at the template and probably a fair amount of customized code.