---

14.1 建立用户定义的 VB 函数

函数的一般格式如下：

Public  Function functionName (Arg As dataType,..........) As dataType

或

Private  Function functionName (Arg As dataType,..........) As dataType

* Public表明该函数是适用于整个程式，

   Private 则表明该函数只适用于某个模块或子程序。
 

范例 14.1

图14.1

程序代码

Public Function FV(PV As Variant, i As Variant, n As Variant) As Variant

End Function

Private Sub compute_Click()

Dim FutureVal As Variant
Dim PresentVal As Variant
Dim interest As Variant
Dim period As Variant
PresentVal = TxtPV.Text
interest = TxtRate.Text
period = TxtYears.Text

FutureVal = FV(PresentVal, interest, period)
LblFV.Caption=FutureVal

End Sub

　

　

范例 14.2

以下函数将自动计算学生获得的考试分数和等级，输出屏幕如图14.2 所示。

图14.1

程序代码

Public Function grade(mark As Variant) As String
Select Case mark
Case Is >= 80
grade = "A"
Case Is >= 70
grade = "B"
Case Is >= 60
grade = "C"
Case Is >= 50
grade = "D"
Case Is >= 40
grade = "E"
Case Else
grade = "F"
End Select

End Function

Private Sub compute_Click()

Lbl.Caption = grade(txtMark)
 

End Sub