模块级变量 出错 。请帮忙看下。

Dim a As Double
a = Val(Form1.Text1.Text)

Private Sub Command1_Click()
Text2.Visible = True
Text2.Text = Fix(a)
End Sub

Private Sub Command2_Click()
Text2.Visible = True
Text2.Text = Int(a)
End Sub

Private Sub Command3_Click()
Text2.Visible = True
Text2.Text = Abs(a)
End Sub

Private Sub Command4_Click()
Text2.Visible = True
Text2.Text = Sgn(a)
End Sub

Private Sub Command5_Click()
Text2.Visible = True
Text2.Text = Sqr(a)
End Sub

Private Sub Command6_Click()
Text2.Visible = True
Text2.Text = Exp(a)
End Sub

Private Sub Form_Load()
Text1.Text = ""
Text2.Text = ""
Text2.Visible = False
Command1.Caption = "fix(x)"
Command2.Caption = "int(x)"
Command3.Caption = "abs(x)"
Command4.Caption = "sgn(x)"
Command5.Caption = "sqr(x)"
Command6.Caption = "exp(x)"
End Sub
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a = Val(Form1.Text1.Text) 插到每个单击事件中就有用了  。就不知道为什么 “模块的通用声明段”