A Journal has to be posted or not to create DFF in any of the journal's block?
And how do we go about if we have to create for a whole batch of Journals?
And last,can I use the same steps to create DFF on a Custom built form?

Thank You

Sorry I dont think I understood your question completely.
Here are some points:
1) DFF has nothing to do posting.
2) You can enable DFF on most screens. The way to tell is that will see a DFF symbol [] (bear mug) on the screen. That means DFF could be enabled.
3) You can enable DFF on Enter Journal screen.
4) While enabling DFF you define the DFF fields. These DFF fields popup on the screen. For example:
CAPITAL EXPENDITURE (YES/NO)
PROJECT (P1/P2/P3)
5) You can define if the fields would be mandatory or not.
6) You can even define context sensitive field. For example:
If the journal category is Adjustments then following fields would appear:
ADJUSTMENT REASON:
APPROVED BY:
If the journal category is Invesmtent then following field would appear:
INVESTORY:
7) If a custom form is build using Oracle standards then you can enable DFF in custom forms as well. However you should not get to that point in an ideal world. If you need an extra field then you should be able to incorporate that directly in your custom form as a regular field. orry I dont think I understood your question completely.
Here are some points:
1) DFF has nothing to do posting.
2) You can enable DFF on most screens. The way to tell is that will see a DFF symbol [] (bear mug) on the screen. That means DFF could be enabled.
3) You can enable DFF on Enter Journal screen.
4) While enabling DFF you define the DFF fields. These DFF fields popup on the screen. For example:
CAPITAL EXPENDITURE (YES/NO)
PROJECT (P1/P2/P3)
5) You can define if the fields would be mandatory or not.
6) You can even define context sensitive field. For example:
If the journal category is Adjustments then following fields would appear:
ADJUSTMENT REASON:
APPROVED BY:
If the journal category is Invesmtent then following field would appear:
INVESTORY:
7) If a custom form is build using Oracle standards then you can enable DFF in custom forms as well. However you should not get to that point in an ideal world. If you need an extra field then you should be able to incorporate that directly in your custom form as a regular field. The whole idea of DFF is that you are able to add extra fields into Oracle screens without programming. You are programming your custom form anyways then why not add those extra fields there directly.