calculating formula only on active rows

Thanks.

Maybe like this, assuming the data starts in A7:

Sub CI_calculation()
    With ActiveSheet.Shapes("Button 7").TextFrame.Characters
        .Text = "CI"
        With .Font
            .Name = "Arial"
            .FontStyle = "Regular"
            .Size = 10
        End With
    End With

    With Range("A7", Range("C7").End(xlDown)).Offset(, 3)
        .Columns(1).FormulaR1C1 = "=SQRT(1/RC[-1])"
        .Columns(2).FormulaR1C1 = "=RC[-3]-1.96*RC[-1]"
        .Columns(3).FormulaR1C1 = "=1+1.96*RC[-2]"
    End With
End Sub