thank you for your reply, in fact your suggestion i have tried it before, i know it can work but my situation is like this :

(front end application)

txt1.text = "Something"
txt2.text = ""

if txt2.text = "" then i want to convert it to NULL, then insert into table using following statement.

sql = "Insert into tablename (field1,field2) values ('" & txt1.text & "', " _
& "'" & txt2.text & "')"

is it possible to do so ?