error in inserting into db

hi all

This is my sql query and it cuase error when the "dimand" felid is empty.

strsql = "insert into  user (name ,no_parvande, tel, c_post, s_post, mail, add, tarefe, dimand)  VALUES ("
strsql = strsql & "'" & name & "' , "
strsql = strsql & "'" & no_parvande & "' ,"
strsql = strsql & "'" & tel & "' ,"
strsql = strsql & "'" & c_post & "' ,"
strsql = strsql & "'" & s_post & "' ,"
strsql = strsql & "'" & mail & "' ,"
strsql = strsql & "'" & add & "' ,"
strsql = strsql & "'" & tarefe & "',"
strsql = strsql &  dimand  & ")"

dimand type is numeric and the others have text type.

please help me

thx for ur help

i use access db,and i set the fileld property to "not required"

but it cuase syntax error  when i'm testing my query result in access(as a query in sql view)

can anyone tell me how to change my query to do right with empty filled?