I think this will serve your purpose.

Code:
Sub FillFormula()
    
    Dim rngFillRange    As Range
    
    'Assuming Data is in column A and formula you want in column B
    'Making Dynamic range for filling the data
    'Let say Your first Formula exists in B1 then
    
    Set rngFillRange = Range("B1:B" & Range("A" & Rows.Count).End(xlUp).Row)
    rngFillRange.FillDown

End Sub


HTH
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