Hello there

I am new at MT4 scripting, so please forgive me if I am asking a stupid thing...
I am testing few EAs, and what I would like to do, is export current account balance (and optionally daily change) to a .csv or .txt file, once every day (at 00:01 for example)...
I tried writing a script that would do that, but although i was looking for examples, i did not get past this:

int start()
{
//----
int handle;
handle=FileOpen("my_data.csv",FILE_CSV|FILE_READ,' ;');
if(handle<1)
{
Print("File c:\my_data.dat not found, the last error is ", GetLastError());
return(false);
}
balance=DoubleToStr(AccountBalance(),2);

//----
return(0);
}
//+---------


So, I know how to open a file and how to get balance... But how to write it the end of file?
And how to run this at exact time, but only once daily?

thanks,
Jaka