如何在特定列或多个列中更改多个公式

I have an excel sheet in which there are 100 rows and 20 columns. If I want to change the formula from "=SUM" to ="AVERAGE" just for the cells that are present in Column B, without affecting any other columns that might also have "=SUM" formula in them, then how to do that ?I have an excel sheet in which there are 100 ro