Thank u all the guys & your valuable info., I did sort out the problem was that the combo box need to requery each time the record move, and now I solve the problem by replace the combo box with text box although it is less flexible for users but it worth it.

Now I also have a problem with the report. It show out fast enough in local pc, however when other pc need to print out the report, it is really slow. I use report Data Env. Filter property to filter the records. any commend??

Thank u.