Transferring a file path from Windows form to function - winforms

Question

I'm quite a novice when it comes to user interface development in C ++. Until now I have always started in the Command Window my program.
To start a program I've used the following call.
Prg.exe -slicesize 3 -infill 5 -model cube.stl -ascii -eulerangles 0 0 0
This was processed using the following code
for (int i = 1; i <argc;) {
    if (0 == strcmp (argv [i], "-slicesize")) {
        slice size = atof (argv [i + 1]);
i + = 2;
    }
else if (0 == strcmp (argv [i], "-infill")) {
infill = atof (argv [i + 1]);
i + = 2;
}
    else if (0 == strcmp (argv [i], "-model")) {
        strcpy (model file name, argv [i + 1]);
        i + = 2;
    }
    else if (0 == strcmp (argv [i], "-ascii")) {
        isBinaryFormat = false;
        i + = 1;
    }
    else if (0 == strcmp (argv [i], "-eulerangles")) {
        eulerAngles.x = atof (argv [i + 1]);
        eulerAngles.y = atof (argv [i + 2]);
        eulerAngles.z = atof (argv [i + 3]);
i + = 4;
    }
    else {
        ++i;
    }
}
The given file, a .stl file, was than processed to a triangle mesh.
TriangleMesh mesh;
if (stlToMeshInMemory(modelFileName, &mesh, isBinaryFormat)!=0)
return 1;
Here, the selected file but must be in the same folder as the program. But the finished program must be dynamic.
Now I have to develop a user interface. For that I have created in my project a button that opens a OpenFileDialog. The path to the selected file is displayed here in a text box.
private: System::Void button3_Click(System::Object^ sender, System::EventArgs^ e) {
OpenFileDialog^ openFileDialog1 = gcnew OpenFileDialog;
openFileDialog1->InitialDirectory = "c:\\";
openFileDialog1->Filter = "stl files (*.stl)|*.stl|All files (*.*)|*.*";
openFileDialog1->FilterIndex = 1;
openFileDialog1->RestoreDirectory = true;
if( openFileDialog1->ShowDialog() == System::Windows::Forms::DialogResult::OK)
{
textBox1->Text = openFileDialog1->FileName;
}
}
With this code I can search for files and let me see the path. But how can I pass the file name to the function stlToMeshInMemory?
Another question would be to what file I need to program my functions. I use Visual Studio 2012 and have in my project currently three files. Until now I have found the following. In myForm.h [Design] I can make the surface. In myForm.h I program, what should happen when a control element is actuated. In MyForm.cpp I so far only
#include "myForm.h"
using namespace System;
using namespace System :: Windows :: Forms;
[STAThread]
void main (array <String ^> ^ arg) {
Application :: EnableVisualStyles ();
Application :: SetCompatibleTextRenderingDefault (false);
Project2 :: MyForm form;
Application :: Run (% form);
}
Do I have to write the entire program that I've developed in MyForm.cpp? The aim is to read a file and when a button "Translate" is operated to output a file.