主题：如何用一个文本框加载字符型或数值型数据?

想在窗口"textbox1"中无论输入字符型或数值型数据,都能从外部表(access数据库)"表A"加载数据:

Dim txt As String = e.Form.controls("TextBox1").Text

If txt = "" Then

    DataTables("表A").LoadFilter = "[_Identify] Is Null"

Else

    DataTables("表A").LoadFilter = "[收款单位] Like '%" & txt & "%' Or [付款单位] Like '%" & txt & "%' Or [摘要] Like '%" & txt & "%' Or convert([金额],'system.string') = " & txt & ""

    DataTables("表A").Load

End If

提示convert函数无效.应该怎样写代码?