MetaStock -> Tools -> Indicator Builder -> New
Copy and paste formula below.


===
EMA
===
---8<---------------------------

{ Exponential Moving Average v2.2 }
{ EMA periodicity shortens on low bar count }
{ ©Copyright 2003-2004 Jose Silva }
{ http://www.metastocktools.com }

pds:=Input("EMA periods",1,2520,21);
x:=Input("use Open=1 High=2 Low=3 Close=4 WClose=5 P=6",1,6,4);
shift:=Input("EMA vertical shift %",
 -100,100,0)/100+1;
plot:=Input("[1]EMA,  [2]Crossover signals",
 1,2,1);

x:=If(x=1,O,If(x=2,H,If(x=3,L,If(x=5,WC(),If(x=6,P,C)))));
pds:=If(pds>Cum(IsDefined(x)),
 Cum(IsDefined(x)),pds);
Ema:=x*2/(pds+1)+PREV*(1-2/(pds+1));
Ema:=Ema*shift;
signals:=Cross(x,Ema)-Cross(Ema,x);

If(plot=2,signals,Ema)

---8<---------------------------


http://www.metastocktools.com