有程序代码如下：

Private Sub Text1_Change(Index As Integer)
Dim r As Single, L As Single, S As Single, pi As Single
pi = 3.14159
Select Case Index
Case 0
r = Val(Text1(0).Text)
L = 2 * pi * r
S = pi * r * r
Text1(1).Text = Str(L)
Text1(2).Text = Str(S)
Case 1
L = Val(Text1(1).Text)
r = L / 2 / pi
S = pi * r * r
Text1(0).Text = Str(r)
Text1(2).Text = Str(S)
Case 2
S = Val(Text1(2).Text)
r = Sqr(S / pi)
L = 2 * pi * r
Text1(0).Text = Str(r)
Text1(1).Text = Str(L)
End Select
End Sub

当我在文本档1(0)中(即给r赋值)输入10时，就会出现如下图所示的错误提示，请问各位，应该怎样解决呢？谢谢！