formula works in cell but doesn't work in vba

hye....what is the error in this code??? when i try this formula in cell, it works

=INDIRECT("X" & ROW() - 1)

but when i apply in macro, it shows error... can anyone help me to sort it out?? thank you...

Sub celldown()
Workbooks.Open filename:=Range("E6")
Range("X2:X700").Formula = "=INDIRECT("X" & ROW() - 1)"

End Sub