急...Visual Basic编程问题

我做了一个二次函数分析器,代码如下:

Private Sub Command4_Click()
Dim a
Dim b
Dim c
Dim h
Dim i
Dim xa
Dim xb
Dim x
Dim y
Dim m
Dim n
Dim r
Dim fm
Dim fn
Dim fa
Dim fb
If Text1.Text = 0 Then
Label1.ForeColor = &HFF&
Label1.Caption = "二次项系数不能为0！"
Else
a = Text1.Text
b = Text2.Text
c = Text3.Text
Label1.ForeColor = &HFF00&
Label1.Caption = "输入正确，以下显示结果："
h = b * b - 4 * a * c
x = -b / (2 * a)
y = -h / (4 * a)
Text4.Text = h
Text8.Text = x
Text9.Text = y
If h >= 0 Then
i = h ^ 0.5
xa = (-b - i) / (2 * a)
xb = (-b + i) / (2 * a)
Text5.Text = i
If xa < xb Then
Text6.Text = xa
Text7.Text = xb
Else
Text6.Text = xb
Text7.Text = xa
End If
Else
Text5.Text = "不存在"
Text6.Text = "不存在"
Text7.Text = "不存在"
End If