Hi,

Assuming this question still needs an answer and the cell you want the formula placed is the active cell; try this:
ActiveCell.FormulaR1C1 = "=LOOKUP(2,1/((R[19]C[9]>=Sheet2!R2C2:R25C2)*(R[19]C[9]<=Sheet2!R2C3:R25C3)),Sheet2!R2C6:R24C6)"