Issue with Screen Handling at run time

Hi Guys,

I have to apply few handling on screen based on drop down values:

1. How to maintain value in drop down list (Exa - Yes/No)

2. On selecting value Yes or No, I need to enable and disable the field in screen

3. How can I refresh all fields of screen on selecting values from dropdown

4. How can I create F4 help values after selection property as Object Value selector for custom fields

Please advise.

For example:

Here as shown in the screen shot below I need to disable 1. Parking space level & 2. Vehicle registration number once the check box "Parking space disabled" is checked.

Please provide your assistance.

Regards

Nitin