VBA for automatic formula calculation in the range of cells after cell value input

[fotodj]

I am looking for the code working on change of value basis, which does the following: after I type number in col A, column B would show 5% tax calculation and column C total with tax,
I know that I can use formula in Col B =A1*0.05 and =A1+B1 in Col C but I have to copy the formulas and drag it down every time new row is added, I would like to automate that process...

 

[mrshl9898]

Assuming you have formulas in there already, starting in row 1. You can paste this macro into the sheet (not in a module).

If a change is made in column A it will copy the formulas in B1 and C1 down to the last row.

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim KeyCells As Range
    Dim sht As Worksheet
    
    Set sht = ActiveWorkbook.ActiveSheet
    Set KeyCells = Range("A:A")
    
    If Not Application.Intersect(KeyCells, Range(Target.Address)) _
           Is Nothing Then
    lastrow = sht.Cells(sht.Rows.Count, "A").End(xlUp).Row
    Range("B1:C1").Copy Range("B1:C" & lastrow)
       
    End If
End Sub

 

[fotodj]

Thank you mrshl9898 , that code works very well!