写vb程序，转换方法为：〔90，100〕为 A，〔80，89〕为 B，〔70，79〕为 C，〔60，69〕为 D，60以下为 E。

Dim a As Integer
a = Text1.Text
If a < 0 Or a > 100 Then
MsgBox "请输入100以内的数"
Exit Sub
End If
Dim b As String
Select Case a \ 10
Case 0 To 5
b = "E"
Case 6
b = "D"
Case 7
b = "C"
Case 8
b = "B"
Case 9 To 10
b = "A"
End Select

MsgBox b

假设待转换的数为text1输入，单击command1按钮开始转换,转换结果放在text2中。代码如下：
Private Sub Command1_Click()
Dim x as Single
x=Val(Text1) '若不是由text1输入，请改这里
Selcet Case x
Case Is>=90 And Is<=100:Text2="A"
Case Is>=80 And Is<90:Text2="B"
Case Is>=70 And Is<80:Text2="C"
Case Is>=60 And Is<70:Text2="D"
Case Else:Text2="E"
End Select