University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 SESSION 16 VBA example

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Exercise 10.1 You are going to use VBA to create a simple calculator to multiply 2 numbers and display the answer.

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Outcomes To further understand examples of VBA code in Microsoft Access

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Setting up the objects Open a new database and call it vba.mdb Create a new form in design view Add a label with a caption Easy Calculator Add 2 textboxes, one called txtFirst and the second txtSecond, with captions of First number, Second number respectively.

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Add a button Add a command button called cmdCalculate Add a text box called txtDisplay Open the form in code view Select cmdCalculate and onclick

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Assign 3 variables, firstNo,secondNo and Answer as single Set the focus to the txtFirst Assign firstNo to the txtFirst.text firstNo=val(txtFirst.text) (val changes text input to a number)

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Repeat for txtSecond Write code for the answer Assign Answer to txtDisplay.text Test your code by opening the object view the form view

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 The number calculator: form view The number calculator: form view

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 To enter VBA code go to View Code. The 2 drop down boxes at the top contain the objects (LHS) and their associated events (RHS)

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 The code view object event

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Code for number exercise Option Explicit Private Sub cmdCalculate_click() Dim FirstNo As Single Dim SecondNo As Single Dim Answer As Single txtFirst.SetFocus FirstNo = Val(txtFirst.Text) This forces the program to check for inconsistencies This is the code for a procedure (set of functional statements) to perform a calculation when a button is pressed. In Access VBA you need to set the focus on the object

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 'decision construct to check that a positive no is entered If FirstNo < 0 Then txtFirst.Text = "" MsgBox "You must enter a positive no" txtFirst.SetFocus End If FirstNo = Val(txtFirst.Text) End Sub

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Code for the above Exercise: this must be typed into the design view of the NumberCalculator form (view code) Option Compare Database Private Sub cmdCalculate_click() Dim FirstNo As Single Dim SecondNo As Single Dim Answer As Single txtFirst.SetFocus ‘This appears by default when you open the code screen – it forms part of the General Declarations area. FirstNo = Val(txtFirst.Text) 'decision construct to check that a positive no is entered If FirstNo < 0 Then txtFirst.Text = "" MsgBox "You must enter a positive no" txtFirst.SetFocus End If

University of Sunderland CIF 104 Fundamentals of DatabasesUnit 16 Code continued FirstNo = Val(txtFirst.Text) txtSecond.SetFocus SecondNo = Val(txtSecond.Text) If SecondNo < 0 Then txtSecond.Text = "" MsgBox "You must enter a positive no" txtSecond.SetFocus End If Answer = FirstNo * SecondNo txtOutput.SetFocus txtOutput = Answer End Sub