i think you can handle this through some color techniques.
On the expression tab , expand the expression properties by hitting the '+' sign. On the background color you can enter a color condition to evaluate if the month is <= or > then the current month. Use the ARGB() color function to assign a transparent color if its in the future.
for example , the following assigns grey color for months <=9 and invisible for months > 9. You would not hard code the number , but perhaps use something dynamice like month(Today()) or month (max(Date)) in its place
if (Month <= 9 , rgb(125,125,125), ARGB(0,125,125,125))
it will still calculate but the lines in the future will not be visible to the user.
attached i added a dynamic example showing the technique
sales to YTD.qvw 199.2 K