Question

I would like to make an excel with VBA file which gets an input from the user 1,2 or 3 :

1. How can I run it while opening the xslm file ?

2. Assuming I have this table in my file:

the common data is useful for column A B and C unique content.
I would like to use the code bellow, so depends on the user input, it will select the unique data from A,B or C to the place of A's unique data. BUT I want that the data of column A will be reusable for future use, e.g. if the user will provide input_num=1 so the data will be A's unique data

Sub main()
MsgBox ("welcome")

Dim input_num As Integer

input_num = InputBox(Prompt:="please select device", Title:="select device", Default:=3)

If input_num = 1 Then

    ' use the first column

ElseIf input_num = 2 Then

    ' use the second column

Else

    ' use the third column

End If

End Sub

Answer 1

1. How can I run it while opening the xlsm file ?

2. Using the column based on User input

To run the code when the Excel file starts you can use

Private Sub Workbook_Open()

End Sub

Any code that you will put here will run provided macros are enabled in your file. For example, you will see a message box “Hello World” when you open the file which has the below code.

Private Sub Workbook_Open()
    MsgBox "Hello World"
End Sub

The Workbook_Open() goes in the Workbook Code area as shown in the screenshot below

Now regarding your 2nd question

In Excel, you can refer to columns not only by names but also numbers so for example

Column A can be referred to as

Sheets("Sheet1").Columns("A:A")

or

Sheets("Sheet1").Columns(1)

This makes your job easier as you can now directly refer to the column based on the user input. For example

Private Sub Workbook_Open()
    MsgBox "welcome"

    Dim input_num As Variant

    input_num = InputBox(Prompt:="please select device", _
    Title:="select device", Default:=3)

    Select Case input_num
        Case 1, 2, 3
            With Sheets("Sheet1").Columns(Val(input_num))
                '
                '~~> Do what ever you want
                '
            End With
    End Select
End Sub