range selection for autofill

hey, I have some noobiesh question, it's probably been answered before in some way but I have been searching it but haven't been able to find it.

I want to autofill some range with some formula and I'm using these lines.

Selection.AutoFill Destination:=Range("B1:B10"), Type:=xlFillDefault
Range("B1:B10").Select

only I would like to be able to adjust the range depending on the size of the dataset. so I would to be able to set a number in a cell i.e. A1=20 so that the code changes to

Selection.AutoFill Destination:=Range("B1:B20"), Type:=xlFillDefault
Range("B1:B20").Select

try this one

Sub autofill()
    Dim i As Long
    i = InputBox("Enter the last row number")
    
    Selection.autofill Destination:=Range(Cells(1, 2), Cells(i, 2)), Type:=xlFillDefault
    Range(Cells(1, 2), Cells(i, 2)).Select

End Sub