As @ScottWe mentions: you're trying to apply PLSQL logic in HTML/javascript. The 'When - Condition' is evaluated at runtime and thus you can't use PLSQL there.
The date arithmetic is a bit annoying in javascript though, so if you're a unfamiliar with it, here is a way you can perform your check (which is, is the entered date tomorrow or not).
Taking my clues from these:
Date difference in Javascript (ignoring time of day)
JavaScript how to get tomorrows date in format dd-mm-yy
Add this function to the page's javascript section for global variables and functions:
function isTomorrow(pDateItem){
function getTomorrow(){
var tomorrow = new Date();
tomorrow.setDate(tomorrow.getDate() + 1);
return tomorrow;
};
function cutTime(pDate){
return new Date(pDate.getFullYear(), pDate.getMonth(), pDate.getDate());
};
// check if pDateItem leads to a selection
// check if it is a datepicker
// check if a date has been selected
if ( $(pDateItem).length
&& $(pDateItem).data("datepicker")
&& $(pDateItem).datepicker("getDate") !== null
)
{
var tomorrow = getTomorrow();
var check = $(pDateItem).datepicker("getDate");
var one = cutTime(check);
var two = cutTime(tomorrow);
return one.getDate() === two.getDate();
};
return false;
}
Then in your Dynamic action 'When' condition, use a javascript expression with this code:
isTomorrow(this.triggeringElement)
Then the corresponding True Actions will only fire when the date is set to tomorrow.