Enter a query in a default value expression - jasper-reports

Question

In Jasperreports I would like to enter a Default Value Expression to a Parameter as a Query string to be able to dynamically provide the user with a default value that is correct, but not force him to choose it.
Is there anyway?
I guess the result should look something like this (even though it doesn't work):
I am using this for a form with a single-value selection method (the user can write which ever number he/she wants but I want the default value to be selected from the database).

Answer 1

Here's how I handle this:
The user selects a value from an input control (in my example, I will call it $P{time_toggle}). Then, I have another parameter ($P{time_constraint}) that takes the user input from $P{time_toggle} and decides what SQL string to inject into the main query based on it. The default value expression for $P{time_constraint} looks like:
$P{time_toggle} == "rolling_quarter" ? "..." : (
$P{time_toggle} == "rolling_30_days" ? "..." : (...
)
)
Then, in my main report query I reference $P{time_constraint}:
SELECT * FROM tblTable WHERE $P!{time_constraint}
To set a default time period, I set the default value expression for $P{time_toggle} to my desired default.