Hi .. it is not possible to create a custom formula using the 30 minute time frame using TI Pro - you can only create formulas using existing data - for Bollinger Bands, that is 15 and 60 minutes.
However, TI will be offering a way in which you can create any strategy that you can think of - which would allow you to use a 30 minute time frame for Bollinger Bands. I cannot tell you exactly when that will be.