Fixed column width

Hi,

I'm trying to create a vb to get all columns on my sheet to have a fixed width.
If I run my sub all columns go back to the set width. But I want the width to reset when the width is changed.

Sub HeightWidth()

    Columns("A:C").ColumnWidth = 20
    Columns("D:D").ColumnWidth = 12
    Columns("E:F").ColumnWidth = 16
    Columns("G:G").ColumnWidth = 8
    Columns("H:H").ColumnWidth = 12
    Columns("I:M").ColumnWidth = 3
    Columns("N:N").ColumnWidth = 7
    Columns("O:O").ColumnWidth = 45

End Sub