[amibroker] If or IIf or How?

[crashoz]

I wish to create an Array (Array XY) where the first "10" bars are 
the "Close" price of that bar and then the rest (from bar 11 on) are 
a formula that includes the previous bars value in that formula.

For example 

Bars 1-10 = Close
Bars 11 to Current Bar = (Close + Ref (Array XY, -1)) / 2

Please note that above is not the formula but an example to make it 
simpler.I have tried If and IIf Statements but no luck as yet.


I am trying to convert the below part of a TradeStation formula to 
afl.
"//
Input: Price(numericeseries), Period(numericsimple);

Vars: Mm (0);

If (currentbar <= period) then mm = Price;

If(currentbar > period) then mm = (mm[1] + price)/2;

ADP = mm;
End;
//"


I am at a loss, any direction would be great.
Crashoz