Yes. I did revise my question since I did not expect to get answer so fast. Sorry about that.
For the clear form question, I use the requery() function to execute the query so that the results can be refreshed every time clicking the Clear Button. The query is "Select ID, Name, Date from Maintable where Name like form!searchform!name_combo......"
The ID, Name, DateRecv fields of the query are displayed in the search form as well as the search criteria (such as textboxes that users can input). To set the textbox = null could clear all the values of those search criteria textboxes . However, it will give me an error when I set the ID = null, Name = null, and DateRecv = null.