Lesson 11: Introduction to VB Functions- Part II

11.1 Creating Your Own Functions

The general format of a function is as follows:

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

or

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

* Public indicates that the function is applicable to the whole program and
Private indicates that the function is only applicable to a certain module or procedure.

Example 11.1

In this example, a user can calculate future value of a certain amount of money he has today based on the interest rate and the number of years from now(supposing he will invest this amount of money somewhere). The calculation is based on the compound interest rate.

Public Function FV(PV As Variant, i As Variant, n As Variant) As Variant
'Formula to calculate Future Value(FV)
'PV denotes Present Value
FV = PV * (1 + i / 100) ^ n

End Function

Private Sub compute_Click()
'This procedure will calculate Future Value
Dim FutureVal As Variant
Dim PresentVal As Variant
Dim interest As Variant
Dim period As Variant
PresentVal = PV.Text
interest = rate.Text
period = years.Text

FutureVal = FV(PresentVal, interest, period)
MsgBox ("The Future Value is " & FutureVal)
End Sub

Example 11.2

The following program will automatically compute examination grades based on the marks that a student obtained.

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()

grading.Caption = grade(mark)

End Sub

Private Sub End_Click()
End

End Sub