SQL & PL/SQL :: How To Fetch Values From Other Tables In Application On-submit Process

In Oracle Apex 4.1,The Leave_transaction Table has the following Fields,

1.Leave_id
2.Emp_name
3.From_date
4.To_date
5.Remaining_days

The Emp_Master Table has the following columns,

1.Emp_id
2.Emp_Name
3.Remaining_days

Holiday_master table has the list of holiday dates as "From_Date"

I have the form based on the Leave_Transaction Table, and I have created the Process, as "On-submit-after computations and validations" and posted the following PLSQL code,

declare
days number(3);
ex_days emp_master.remaining_days%type;
new_rem_days emp_master.remaining_days%type;
begin

[code]....

If the Dates is between from_date and To_date comes in Saturday and sunday and/or if any Date is exist in the Hpliday_master table it will exclude and return the count(*) remaining dates, For example,

If the From_date is 04-may-2012' and To_date is 08-may-2012,

Here the dates 5th may and 6th may are "saturday" and "sunday"

and if any date between From_date and To_date is exist in Holiday_Master Table i.e say here it is 07-may-2012, Then the remaining dates are(excluding sat,sunday and dates in holiday_table),

04-may-2012,
08-may-2012.

so the count(*) is 2.

I am using the above code but still it returning 5,I think this

...where to_char(dt,'fmday') not in ('sunday','saturday') minus (select holiday_start from holiday_master))

code is not working.