如何遍历字符串并检查每个字符的字节值？

Code I have:

我有以下代码：

        cell_val = CStr(Nz(fld.value, ""))
        Dim iter As Long
        For iter = 0 To Len(cell_val) - 1 Step 1
         If Asc(Mid(cell_val, iter, 1)) > 127 Then
           addlog "Export contains ascii character > 127"
         End If
        Next iter
        cell_val = CSt