For i = -$(vLookbackLength) to -1 Trace $(i); Next i Will trace -27 to -1 as Month(today()) =3 (March).
Try this instead For j = 0 to 24 //or 23 depending on if you include current month as one of the 24 months Let vPeriod = MonthName(today()-$(j)); Trace $(vPeriod); Next
It should trace all moths from the current to February 2018.