Leave types getting collision when applied from r3 in 2001 by time admin

hi,

employee applied leave from portal , went to manager for approval .....manager did not take any action ....time admin booked the same leave in 2001 , later manager went to portal and tried to approve the same leave .....getting error " conflict with absence followed by leave type the same which is already booked by time admin .....my requirement is when MSS user is trying to approve the leave if he is rejects it getting delete from his tasks UWL and going mail to employee stating that the leave is approved by mss user from portal ...but that is already approved by time admin in 2001 infotype ....i want solution is there is any snote to overcome this process ....i have suggested to go to ptarq and go to rptarqdbdel ......and select the period and delete the document which is in "sent" status .....it will get delete from mss user portal uwl task .......all experts suggest me how to achieve this tasks