automatic buy/sell ?

Dear huseyin, you can simply use "pending order" type of transaction.

let say you want to buy at 1.345 then you can use "pending order" instead of "market order" and put the 1.345 on the price. Then the MT4 will automatically perform your order when the price hit 1.345 otherwise it will remain open.

you can also create simple forex expert advisor for that

to put the pending order is risky thing... You cannot be 100% sure, that the market conditions will be applicable for opening trade, when the price will achieve value, you set up for pending order. So really, the simple EA is better option