3 RichTextBoxes

I have created 3 RichTextBoxes, a label and a Button.

As the code goes, if I write a number in RichTextBox 2 and another in RichTextBox3 and press the Button.
These will be added and show a result in the label. (Ex: 5 + 3 = 8)

Now I wonder for a function here. I will add another "RichTextBox1" that will make a statement like:

if 3 = 3 (wich is true ofcourse)

then the calculation for in the example (5 + 3) will execute otherwise not !

How could this be possible. Is it possible to use a bool for RichTextBox1 in any way here and if what is written in RichTextBox3 is True like:
3 = 3 then it continues with the code below to Add (5 + 3) ?
This code is working for RichTextBox2 and 3 as a calculator:

Code:

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double FirstValue = double.Parse(richTextBox2.Text);
double SecondValue = double.Parse(richTextBox3.Text);

double result = 0;

result = FirstValue + SecondValue;

label1.Text = result.ToString();

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