求vb大神帮忙，怎么使用统计函

Asc(Str) 返回字符的编码：
dim tmp as string
dim a%,b%,c%,d%
for i=1 to len(text1.text)
tmp=mid(i,1)
if tmp>=asc("A") and tmp<=asc("Z") then
a=a+1
elseif ...
....

谢谢

Private Sub Command1_Click()
Dim tmp As Integer
Dim a%, b%, c%, d%
Dim w As String
t = Len(Text1.Text)
w = Text1
For i = 1 To t
tmp = Asc(Mid(w, i, 1))
If tmp >= Asc("A") And tmp <= Asc("Z") Then
a = a + 1
ElseIf tmp >= Asc("a") And tmp <= Asc("z") Then
b = b + 1
ElseIf tmp >= Asc("0") And tmp <= Asc("9") Then
c = c + 1
Else
d = d + 1
End If
Label3.Caption = "大写字母:" & a & "小写字母:" & b & "数字:" & c & "其它:" & d
Next
End Sub