file searching

hi..im developing an application in which i am writing various files to a specified directory,
with the file name written in dialog box, and the moment Ok on dialog is pressed, a file is generated with that name in the specified directory.

Now i want that whenever a file name is entered in the dialog and ok is pressed then it first checks for the file and if it exists in the directory then a prompt or pop up is displayed "file exists , enter new name", and again we can enter the file name in dialog box.following is the code im using for creating files in directory:

RFile File;
RFs iFs;
TBuf<200>avar;

avar.Copy(_L("C:\\ACM\\lists\\BL_"));
avar.Append(text);
avar.Append(_L(".xml"));
iFs.Connect();
File.Replace(iFs,avar,EFileWrite);
File.Append(text);
//File.Write(aVar1);
File.Close();
iFs.Close();

}

so i want that the directory specified must be checked if a file of the specified name exists or not..