Compound Filtering on an Axis

I have raw data that is time phased. Time is the X Axis. A Line/Column chart allows me to chart the data as columns and then use a custom measure for the line that represents cumulative value of the columns. The problem is the cumulative measure goes horizontal and runs that way for the remainder of the X-axis. I would like a method to stop plotting the value (or change its color) after a date such as NOW, or a keyed date, or a single date divined from a formula