Combine and append text from different richtextBoxes into one richTextBox

Question

Ok guys, so I need some help with a project I am making (no this isn't a school project, yes I'm fairly* new to coding) Before I made this post I searched all over the internet and this site looking for guidance myself and found nothing that was useful to help me do what I want this to do. I made a little layout of what i have vs. what I am trying to accomplish here.

A little text explanation: I want take my keyword textbox(these are all richtextboxes to clarify) which would be textbox1 in the chart, and i want to append text from eachbox to the end of each other until all combinations are added to the end of the 1st item in text box one, then repeat for the second item

Visual explanation:This is my starting point

richtextbox 1          richtextbox2          richtextbox3          richtextbox4


item1textbox1string      item1textbox2string     item1textbox3string     item1textbox4string

item2textbox1string      item2textbox2string     item2textbox3string     item2textbox4string

item3textbox1string      item3textbox2string     item3textbox3string     item3textbox4string

item4textbox1string      item4textbox2string     item4textbox3string     item4textbox4string

this is the outcome desired...

item1textbox1string + item1textbox2string + item1textbox3string + item1textbox4string
item1textbox1string + item1textbox2string + item1textbox3string + item2textbox4string
item1textbox1string + item1textbox2string + item1textbox3string + item3textbox4string
item1textbox1string + item1textbox2string + item1textbox3string + item4textbox4string

after all items complete from listbox2-4 on the first string from textbox one I want to then restart on item 2 from textbox1 and repeat the process for remaining textbox1 items.

item1textbox1string + item1textbox2string + item2textbox3string + item1textbox4string
item1textbox1string + item1textbox2string + item2textbox3string + item2textbox4string
item1textbox1string + item1textbox2string + item2textbox3string + item3textbox4string
item1textbox1string + item1textbox2string + item2textbox3string + item4textbox4string

item1textbox1string + item1textbox2string + item3textbox3string + item1textbox4string
item1textbox1string + item1textbox2string + item3textbox3string + item2textbox4string
item1textbox1string + item1textbox2string + item3textbox3string + item3textbox4string
item1textbox1string + item1textbox2string + item3textbox3string + item4textbox4string

item1textbox1string + item1textbox2string + item4textbox3string + item1textbox4string
item1textbox1string + item1textbox2string + item4textbox3string + item2textbox4string
item1textbox1string + item1textbox2string + item4textbox3string + item3textbox4string
item1textbox1string + item1textbox2string + item4textbox3string + item4textbox4string

item1textbox1string + item2textbox2string + item1textbox3string + item1textbox4string
item1textbox1string + item2textbox2string + item1textbox3string + item2textbox4string
item1textbox1string + item2textbox2string + item1textbox3string + item3textbox4string
item1textbox1string + item2textbox2string + item1textbox3string + item4textbox4string

and so on until textbox 1 items are completed.

then repeat for item 2 and so on...

item2textbox1string + item1textbox2string + item1textbox3string + item1textbox4string
item2textbox1string + item1textbox2string + item1textbox3string + item2textbox4string
item2textbox1string + item1textbox2string + item1textbox3string + item3textbox4string
item2textbox1string + item1textbox2string + item1textbox3string + item4textbox4string

I've included a picture of a program that does what im trying to do essentially. I apologize in advance for the poor format, its hard to type in this thing.

What i'm trying to achieve:

Current Layout:

Answer 1

I created this as a sample for the logic I told you in the comment. By saving the strings into a collection, you can easily manipulate them using iteration:

static void Main(string[] args)
    {
        string[] c1 = { "Mik", "Don", "Sundar", "Neil" };
        string[] c2 = { "Kim", "Joy", "Fred", "Roi" };
        string[] c3 = { "Mae", "LA", "Ej", "Bob" };
        string[] c4 = { "Yin", "Yang", "Ching", "Chong" };

        for (int i = 0; i < 4; i++ )
        {
            string output = "";
            output += c1[i] + " "; 

            for (int j = 0; j < 4; j++)
            {
                string output1 = output;
                output1 += c2[j] + " ";

                for (int k = 0; k < 4; k++)
                {
                    string output2 = output1;
                    output2 += c3[k] + " ";

                    for (int l = 0; l < 4; l++)
                    {
                        string output3 = output2;
                        output3 += c4[l] + " ";
                        Console.WriteLine(output3 + "\n");
                    }
                }
            }
        }
            Console.ReadKey();
    }

Link to Output Strings

It produces all possible combinations of strings. You can also use List to store all strings for each category.