Excel and Visual Basic

Outline Data exchange between Excel and Visual Basic. Programming VB in Excel

Exchange data with.csv file.csv file is “comma separated value” file..csv file is plain text file..csv file can only save one worksheet. For multiple worksheets in a workbook, you need to use several.csv files. You need do some editing to remove titles or labels before you use VB to read it.

Example

Code Private Sub Command1_Click() Dim payment(1 To 50) As Single, commission(1 To 50) As Single Dim index As Integer Open App.Path & "\commission.csv" For Input As #1 index = 1 Do While Not EOF(1) Input #1, payment(index), commission(index) index = index + 1 Loop Close #1 End Sub

Using VB in Excel Excel uses a special version of Visual Basic, which is called Visual Basic for Application (VBA) User can use VBA to create customized Excel function (VBA procedures), which can be much more powerful than the build-in Excel functions.

Security issues VBA procedures in Excel is also called Macros. Macros are two-edged swords. Macros viruses are malicious VBA procedures.

Setting the security level

Security Level High (default) Medium. We should set the security to this level to run our VBA procedure. Low (not recommended)

Medium level security If you set the security level to medium, every time you open a Excel file containing macro, Excel will ask you if you want to enable the macro.

Example

VBA function code Function Comm(Sales_V As Single) as Single If Sales_V =500 and Sales_V =1000 and Sales_V =200 and Sales_V =5000 Then Comm=Sales_V*0.15 End If End Function

Edit VBA program in Excel

Insert modules The VBA procedure should be defined in a module. If you don‘t have an existing module, create one by using the insert->Module menu.

Write code in visual basic editor

Final result

Passing a range of cells to VBA procedure The previous example shows how to pass one value to a VBA function. However, in Excel it is possible to pass several cells to a build-in function. E.g. SUM(a5:a7) We call a5:a7 is a range. User defined VBA function can also get a range of cells as input.

Data type: range VBA defines a specific data type: range Range is just like a object: it has properties. Important properties of range Count : How many cells in the range Value : Value of the cell (it works when range refers to only one cell)

Accessing individual cells We use a special form of For…Next loop to access each cell in a range Function meanvalue(InputRange As Range) As Single Dim cl As Range For Each cl In InputRange ‘some code here to get the value ‘cl.value keep the value of the cell Next cl End Function Red word are key word in Visual Basic

Program task Define a VBA function that calculate the average of a range of cells. We define the function’s name as meanvalue.

code Function meanvalue(InputRange As Range) As Single Dim cl As Range ‘cl is used to get individual cell Dim index As Integer, sum As Long index = 1 ReDim inputarray(1 To InputRange.Count) As Single For Each cl In InputRange inputarray(index) = cl.Value ‘save cell value into array index = index + 1 Next cl sum = 0 For i = 1 To InputRange.Count sum = sum + inputarray(i) Next meanvalue = sum / InputRange.Count End Function

Use your defined VBA function