What actually you are trying to do.
Do you want to create a predefined condition using prompt and then get data for the previous quarter for the date passed in the prompt.
Give more details.
There are several functions that will be useful. First, the trunc() function allows you to truncate a date to a specific date component such as quarter, as in
trunc(date, 'Q')
Then to get the previous quarter you can do add_months() with a parameter of -3 to get the start of the prior quarter, and simply subtract one from the date to get the end of the prior quarter.
Then you can use a case statement looking for tran_date between those two values and return the measure or whatever information you are looking for. If you are just looking for the start date and end date of the prior quarter then the functions I have mentioned should be good enough.
These are all Oracle functions. I am assuming you are using Oracle based on your question related to sysdate in another topic.