哪位大侠帮忙看下这段代码，提示     and物料名称 。。。缺少操作数

Dim t As Table
Dim filter As String
Dim gys As WinForm.ComboBox = e.Form.Controls("供应商")
Dim wlmc As WinForm.ComboBox = e.Form.Controls("物料名称")
Dim qsrq As WinForm.DateTimePicker = e.Form.Controls("DateTimePicker1")
Dim jsrq As WinForm.DateTimePicker = e.Form.Controls("DateTimePicker2")
t= Tables("物料信息")
If gys.Value IsNot Nothing Then
    filter= "供应商= \'" & gys.Value & "\'"
End If
If wlmc.Value IsNot Nothing Then
    If filter> "" Then
        filter= filter & "And"
    End If
    filter= filter & "物料名称= \'" & wlmc.Value & "\'"
End If
If filter> "" Then
    t.Filter= filter
End If