C/C++ :: Change Root Path That Application Uses To Upload File From?

I have an application which is used for calibration for electrical components. Here I want to set a rootpath for this application. I did some research and I found out that I can get the rootpath of the application (that is where the exe is stored) But what I am really looking for is once I start the application the root path should be what I assign. For instance currently the root path is "C:UsersPublicDocumentsABC.ToolsProjects" but I would like the root path to be "E:New ABC" Is this possible? I wrote some code where I call the exe of the application and it opens the file in a folder that I specify :

private void NewJournal_Click(object sender, EventArgs e)
{  
string filePath = @"E:New ABCabc.vnalog"
if (!File.Exists(filePath))
{
return;
}  
string SelectedFile = @"/select, " + filePath;
System.Diagnostics.Process.Start(@"E:New ABCabc.vnalog", SelectedFile);  
}  

Now this code open the .vnalog file in the application. And this works great..!!! How can I now change the path within the application?