为什么我的update语句不能用？

friendmine

在ACCESS2000中我写了下面这段程序
dim rs as new adodb.record
dim conn as new adodb.connection
set conn = currentproject.connection
rs.open "select * from table1", conn,adOpenKeyset, adLockOptimistic
if not rs.eof then
   dim str as string
   str = "UPDATE Table1 SET MemberCode ='dfkd' where MemberCode = 'dfkk'"
   docmd.runsql str
endif
为什么不能更新呢?