求VB大神指导！！这怎么做啊！！后天要交了然而我什么也不会！！炸裂！！

题目太多了，第三个已经做好了
Dim str As String = "MFKFASAVILCLVAASSTQA"
Dim str1 As String = ""
Dim a As Integer
Dim M, C As Integer
C = 0
M = 0
For i = 1 To Len(str)
a = Asc(Mid(str, i, 1))
If a = Asc("M") Then
M += 1
End If
If a = Asc("C") Then
C += 1
End If
Next
str1 = str1 & "蛋氨酸（M）的个数为" & M & " 半胱氨酸（C）的个数为" & C & vbCrLf
str1 = str1 & "蛋氨酸（M）的百分比为" & ((M + C) / Len(str)) * 100 & "%" & vbCrLf
TextBox6.Text = str1