Need help with session state/item refresh

Question

I have an application that allows users to record productivity information for our employees. There are different types of work they have to do, so the form is in header/multiple-detail form and uses collections to handle all processing. In the header portion are the fields that record the time of work. Though this is stored in the database as a single field for start of shift and single field for end of shift, in the entry it is split up into 9 fields: 3 for day, month, and year, and three more each for start hours, start minutes, AM/PM, end hours, end minutes, and AM/PM, which I then concatenate to get the dates to store. The update part works fine. When I go in to display each of these, I have to use an SQL query to retrieve only that section of the time.
The problem I am having is that if the user pulls up several timecards to edit them, it retains these time values from the previous timecard, and due to the way the collections refresh, I can't seem to get either item session state parameter (Only when Null/Always from Source) to achieve the desired result. If I use the Only When Null option, I retain the values from the previous timecard. If I use the Always from Source, the user can't update any of the time-related input.
Can anyone suggest a solution? I've tried a session state process that fires on entry to clear those items and ran into the same problem as using the Always From Source option. There has got to be a way to handle this, but it's got me stumped and my users are clamoring for a fix.
Page initial load
A. Before Header process populates job collection and other collection (not header info), which comes straight from DB table.
B. Data displays for Header (from table) and two detail sections (from collections)
User presses Submit to save changes
1. On Submit Before Processing: updates job and other collections (to preserve changes in case validation fails)
2. Validations check to make sure job codes are valid, date is valid, employee is valid, etc.
3. On Submit After Processing: Writes changes to header from input form, writes changes to job and other from collections to appropriate DB tables
I also have two On Submit After Processing processes to add blank lines - one for each collection. These are triggered via buttons.

Answer 1

Blair:
Does creating a 'before header' process to populate these fields make a difference ? The sql could be something like
select TO_CHAR(TC_START_TIME,'HH') into :P1115_TIME_IN_HH from TC where TC_ID = :P1115_TC_ID;You should set the 'Source Used' back to 'Only when current value in session is null' and the 'Source Type' to 'Static Assignment(....)' and clear out the 'Source value or expression' field.
varad