主题：下拉列表怎么去重复的值

如下控件，我设置了一个数据源表，和过滤条件后，发现有很多重复的值，怎么去除重复的值

Dim cmb As WinForm.ComboBox
cmb = e.Form.Controls("ComboBox1")
cmb.DisplayMember = "approver_id" '设置显示列
cmb.ValueMember = "approver_id" '设置取值列
cmb.DataSource = "ACCOUNTS_APPROVAL_HISTORY" '列表项目来自于客户表
cmb.DataFilter="[date] < '" & Date.Now & "'"

cmb.SelectedIndex=0