Running an EA on non standard time frames

I wrote an EA that scans multiple currencies and multiple time frames and checks for their Ima values.

The EA works fine, but I want to add non standard time frames to the list of time frames I scan (2 and 8 hours), is it possible?

yes

I saw that non standard time frames can be used only on offline charts, but I don't understand how this will work.

Does the offline chart get updated like a regular chart?

yes

Will I need to create the offline charts every time I run the EA?

yes

how do I use an offline chart in my EA?

depending on what you want to do

if you want to call an indicator do what honest_knave's says above

There should not be any need to create offline charts - just make the iMA call.

Example: 

From iMA:

timeframe

[in]  Timeframe. It can be any of ENUM_TIMEFRAMES enumeration values. 0 means the current chart timeframe.

From Enum_Timeframes: 

There should not be any need to create offline charts - just make the iMA call.

Example: 

From iMA:

timeframe

[in]  Timeframe. It can be any of ENUM_TIMEFRAMES enumeration values. 0 means the current chart timeframe.

From Enum_Timeframes: 

wrong

this works only if you have generated the Chart (periodconverter) + you must open the generated chart before you trying to use it

1) you have to create an offline chart (you can use periodconverter)

2) open the (offline) chart (if you don't open the chart it will return 0.0)

3) than you can use your code:

sa1221:

double last_candle_ma_144 = iMA("EURUSD", PERIOD_H2, 144, 0, MODE_SMA, PRICE_CLOSE, 1);