(求助)sql查询语句

有一张表名为cpxx(产品信息表),里面有cpid,cpname,cpprice三个字段,我现在想修改某一cpid对应的cpprice,语句该如何写?下面是我写的语句,不知道是那里错了,运行时提示出错,请各位指点一二,谢谢!
update cpxx set cpprice='" & Text2.Text & " ' where 'cpid ' =(select cpid from cpxx where cpid=' " & Text1.Text & " ') and data>==#" & DTPicker1.Value & "# and data<=#" & DTPicker2.Value & "# group by cpid