how to insert formula in excel using vba

How to insert the formula for th开发者_运维知识库e entire column using vba

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like this?

this is for relative notation RC

Columns("N:N").FormulaR1C1 = "=SUM(RC[1],RC[2])"

Edit:

you could also use this notation (absolute) :

Columns("M:M").Formula = "=SUM(B2:B3)"