vb如何计算文本框中的大写字母，小写字母，数字，其他字符的个数并在picture中输出个数

PrivateSubCommand1_Click()
n=0
m=0
k=0
l=0
aa=0
bb=Text1
DoUntilLen(bb)=0
aa=Asc(bb)
bb=Right(bb,Len(bb)-1)
Printaa
If97<=aaAndaa<=122Then
n=n+1
Else
If65<=aaAndaa<=90Then
m=m+1
Else
If48<=aaAndaa<=57Then
k=k+1
Else
l=l+1
EndIf
EndIf
EndIf
Loop
Picture1.Print"小写字母为";n;"个"
Picture1.Print"大写字母为";m;"个"
Picture1.Print"数字为";k;"个"
Picture1.Print"特殊符号为";l;"个"
EndSub