operation start time in production order

Dear experts,

                     i have a production order which contains 3 operations say 0010,0020,0030. my requirement is that 0030 operation should be started after 12 hours from 0020 production starts. i had maintained quee time of 12 hours in operation 0030.but the operation start time of 0030 is  calculating from the operation end time of 0020 .if i am maintaining OVERLAPPING SYSTEM IS NOT CONSIDERING THE QUEE TIME

    my process is running like this

                                               operation start time                                           operation end time

operation 0020                        12/4/13    08.30.00                                              12/4/13        22.45.00

operation 0030                        12/4/13    20.30.00                                               13/4/13        02.30.00

system is calculating like this

                                               operation start time                                           operation end time

operation 0020                        12/4/13    08.30.00                                              12/4/13        22.45.00

operation 0030                        13/4/13    10.45.00                                               13/4/13        16.30.00

Thanks,

hari krishna