Private Sub Command1_Click()
Dim a#, b#, c#, p#
Me.AutoRedraw = True
a = 3: b = 4: c = 5
Do
a = Val(InputBox("请输入三角形第一条边", "输入", a))
b = Val(InputBox("请输入三角形第二条边", "输入", b))
c = Val(InputBox("请输入三角形第三条边", "输入", c))

If aa Then
p = (a + b + c) / 2 'S＝ √[p(p - a)(p - b)(p - c)] （海伦公式）（p=(a+b+c)/2））
Print "面积:"; (p * (p - a) * (p - b) * (p - c)) ^ 0.5
Exit Sub
Else
MsgBox "你输入的数据构成不了三角形!", vbQuestion + vbOKOnly, "请检查输入"
End If
Loop
End Sub