thanks abhishek for reply. In openerp, i have validated an invoice then one journal entry is created and automatically posted. I want in one case this journal entry to be cancelled and in another case I just want to cancel journal items of this posted journal entry.

Hi Akram, According to accounting standard whenever you approve a invoice it automatically created a posted entries as its become now an accounting stuffs, so over here you have to cancel your invoice journal entry will automatic cancel and for journal items .... whatever invoice line you have created in invoice screen it is only coming in the Journal entry's line items as per accounting standard. I suggest better cancel your invoice n remove the line item which u not want to be in journal items. For this you may use account_cancel module if you not using currently.

Thanks Abhishek for valuable comment. account_cancel module is doing the job for me.