[amibroker] Running Median Calculation Starting at Bar 0

[searnp]

I am trying to calculate a running median that starts at bar 0.

Code:
RM = Median(Close, BarIndex() + 1);

Then I get the following error message:
Error 5. Argument #2 has incorrect type (the function expects different
argument type here)

I am using "Barindex() + 1" to get a running count at each bar to be
used in the median's lookback period. Is there a way to implement this?

Thanks.