记个函数，别人的

'**************************************************
'函数名：gotTopic
'作  用：截字符串，汉字一个算两个字符，英文算一个字符
'参  数：str   ----原字符串
'       strlen ----截取长度
'返回值：截取后的字符串
'**************************************************
Function gotTopic(ByVal str, ByVal strlen)
    If str = "" Then
        gotTopic = ""
        Exit Function
    End If
    Dim l, t, c, i, strTemp
    str = Replace(Replace(Replace(Replace(str, "&nbsp;", " "), "&quot;", Chr(34)), "&gt;", ">"), "&lt;", "<")
    l = Len(str)
    t = 0
    strTemp = str
    strlen = CLng(strlen)
    For i = 1 To l
        c = Abs(Asc(Mid(str, i, 1)))
        If c > 255 Then
            t = t + 2
        Else
            t = t + 1
        End If
        If t >= strlen Then
            strTemp = Left(str, i)
            Exit For
        End If
    Next
    If strTemp <> str Then
        strTemp = strTemp & "…"
    End If
    gotTopic = Replace(Replace(Replace(Replace(strTemp, " ", "&nbsp;"), Chr(34), "&quot;"), ">", "&gt;"), "<", "&lt;")
End Function

用法：
str="中华人民共和国"
gotTopic(str,4)

得到结果：

中华