I saw this in the chat:

03/09/2008 03:27:05 ?zuzi? I cannot understand this "use previous bar value"
03/09/2008 03:28:42 ?filip? It is selected when the current indicator value is not relevant to the opening price
03/09/2008 03:32:33 ?zuzi? Why?  I'm using MA. Where the problem is?
03/09/2008 03:34:35 ?zuzi? MA(21) on a daily chart 
03/09/2008 03:41:27 ?filip? If your MA uses bar closing price its value will be correct at the end of the day. So you cannot use the current MA during the day.
03/09/2008 03:44:30 ?zuzi? It's strange. MT shows the MA all the time.
03/09/2008 03:47:10 ?filip? Yes, but the value is moving up/down when the market moves. The value MT shows is not the MA value for that day. This current MA value will be changed till the end of the day
03/09/2008 03:48:27 ?zuzi? I see. But I can trade using this MA
03/09/2008 03:50:54 ?filip? It is up to you. But it is not a MA(21). It's MA(20days and 7hours)
03/09/2008 03:55:12 ?zuzi? It seems you are right. So I have to use the MA from yesterday, havn't I?
03/09/2008 03:56:53 ?filip? Yes if you want to trade with MA(21, close).
03/09/2008 03:58:58 ?zuzi? But Forex Strategy Builder doesn't use the previous indicator value sometimes
03/09/2008 04:00:12 ?filip? When the Ma is based on price open you have the correct value
03/09/2008 04:01:03 ?filip? Also when you enter the market at the bar closing price.
03/09/2008 04:03:49 ?zuzi? Great. Thank you