Here's a concept I've thought about whilst on holidays: 

Forward reference (shift backwards on charts) and center a Moving Average, then extend and project the last known MA direction into the future. 

This method gets around the no-plot in null (N/A) zone limitation in MetaStock, and can apply to any indicator or oscillator, either on charts or separate windows. 


MetaStock -> Tools -> Indicator Builder -> New -> 
Copy and paste complete formula between "---8<---" lines.

============= 
MA - centered 
============= 
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{ Centered Moving Average - v3.0 } 
{ Uses forward-referencing to center Mov Avg 
  and project future direction.} 
{ Uses hindsight - do not trade! } 

{ ©Copyright 2005 Jose Silva 
  For personal use only. 
  http://www.metastocktools.com } 

{ User inputs } 
fwPds:=Input("Forward-referencing periods  (automatic = -1)",-1,2600,-1); 
proj:=Input("Project last known MA:  [1]Direction,  [2]Value",1,2,1); 
pds:=Input("Mov Avg periods",1,2600,21); 
type:=Input("[1]EMA [2]SMA [3]TmSr [4]Tri [5]Var [6]Vol [7]Wght",1,7,2); 

{ Choose MovAvg type: 
  1 - Exponential MA 
  2 - Simple MA 
  3 - Time Series MA 
  4 - Triangular MA 
  5 - Variable MA 
  6 - Volume adjusted MA 
  7 - Weighted MA } 
ma:= 
 If(type=1,Mov(C,pds,E), 
 If(type=2,Mov(C,pds,S), 
 If(type=3,Mov(C,pds,T), 
 If(type=4,Mov(C,pds,TRI), 
 If(type=5,Mov(C,pds,VAR), 
 If(type=6,Mov(C,pds,VOL), 
 Mov(C,pds,W))))))); 

{ Automatic period-centering } 
center:=LastValue(If(fwPds<0,Int(pds/2),fwPds)); 

{ Forward-referenced MovAvg } 
fwd:=Ref(ma,center); 

{ Last valid MovAvg plot point } 
lastVal:=IsUndefined(fwd) 
 AND Alert(IsUndefined(fwd)=0,2); 

{ Extend MovAvg plot into future null zone } 
xtend:=LastValue(fwd+PREV-PREV); 

{ Restrict invalid initial MovAvg plot } 
movAvg:=Ref(Ref(xtend,pds-1),-pds+1); 

{ Last MA known direction & future projection } 
init:=Cum(IsDefined(movAvg))=1; 
direction:=movAvg+ 
( ValueWhen(1,init OR lastVal,Ref(movAvg,-1)) 
 -ValueWhen(1,init OR lastVal,Ref(movAvg,-2))) 
 *(BarsSince(init OR lastVal)+1); 

{ Plot MovAvg on price chart } 
If(proj=1,direction,movAvg) 

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