Auto Populate Formula to end of series in excel - vba

Question

I am having an issue with a piece of VBA in excel and am looking for assistance.
I require a piece of code to auto populate a formula in excel through a series of data, the series will vary in length and will occupy columns C:I.
I have been using this piece of code without issue for quiet a while:
Sub Auto_Fill_Formula()
Sheets("Sheet1").Select
Dim LstRow As Long
With Sheets("Sheet1")
LastRow = .Cells(.Rows.Count, 1).End(xlUp).Row
.Range("A2:A" & LastRow).Formula = "Formula added here"
Application.CutCopyMode = False
End With
End Sub
However as the formula is being added to the leftmost column it only populates the first cell, cell A2.
How can I modify this code to work when the leftmost column is empty?
Thank you,
Wayne

Answer 1

You can use Find to find the last used row in C:I by searching backwards from row 1. You should also use Option Explicit to pick up typos in variable names (LstRow).
Sub Auto_Fill_Formula()
Sheets("Sheet1").Select
Dim LastRow As Long, r As Range
With Sheets("Sheet1")
Set r = .Range("C:I").Find(What:="*", After:=.Range("C1"), Lookat:=xlWhole, SearchOrder:=xlByRows, _
SearchDirection:=xlPrevious, MatchCase:=False, SearchFormat:=False)
If Not r Is Nothing Then
LastRow = r.Row
.Range("A2:A" & LastRow).Formula = "Formula added here"
End If
End With
End Sub