2 day EMA of force index with thinkscript?

You did not mention exactly what you are trying to scan for. Yes, you want to create an ema based on the ForceIndex indicator in Thinkorswim. But you didn't tell us what sort of pattern you want. The cross above, cross below? Or simply the position of the ForceIndex in relation to the ema. The later is what I included in this scan:

input fiLength = 13;
input maLength = 2;
input maType = AverageType.EXPONENTIAL;
def fi = ExpAverage(data = (close - close[1]) * volume, fiLength);
def ma = MovingAverage(maType, fi, maLength);
# scan signals
plot scan = fi > ma;
#plot scan = fi < ma;

Note that there are user inputs included here so that folks can adapt this to any type of moving average or length they wish to use.