How to launch rxbag or rqt_bag with the --clock option

Hello I am launching the playback of a bag file using rosbag play. Because I want to emulate the clock at the time of recording I use the --clock option along with the use_sim_time=true parameter http://www.ros.org/wiki/Clock The problem is I want tot use rxbag or rqt_bag instead of rosbag play. None of those accept a --clock option. I should I do it? run a clock server independently? How can I do it? Thanks Miguel Update: No one answered my question. If it does not make sense please let me know. Basically, I just want to know how I can emulate the use_sim_time --clock options with rxbag or rqt_Bag. Thanks Miguel