Unfortunately, you have to assign the Popup menu to each item using the Popup Menu property of the item. Also, unfortunately, the Set_Item_Property() built-in does not allow you to set this property at runtime; you must set the property value during design. You can use the JDAPI Java library to dyamically modify your Forms binaries (.fmb). Search the forum on "JDAPI" for information about using this library. If you are not Java proficient, then only option available to you would be to select all of the items you want to use this popup menu and set the property in mass

Thank you so much for your help on this.
Unfortunately I am not a Java guy.
So I am going with the long procedure of assigning the popup for each and every item .
But only thing is I didn't see that like appending the popup menu in seeded forms . The popuup functionality comes as up and tunning in seeded forms.
If i pick a seeded form and delete all un necessary frames and .... and put my custom stuff in there , then its working.

Anyway i am fine for now . Thanks again for your help.

Finally I am able to resolve it . 
I forgot to update this here and now thought it will helpful for others so I am updating it now even though this is old thread.

This is what I did 
1. Right clik on the form name in forms developer. 
2.Open Property palette
3.Click on the subclass field.
4.Choose "Property Class Name " as "Module".
5.Choose "Module" as your form name .

Thats it and right click started working .