how to delete the leave record from buffer

hi ,

when i apply  CL leave on aug 1 and delete it ....and again if i aPPLY on aug 1 PL in the buffer it is not deleting the previous records......i dont want to go to delete documents in this case and in portal i have only change and delete ...but not cancel in leave overview can somone tell me how to have the option like cancel the leave

Regards,

jwala