Saving a value from Text Box

Hi, I have a WPF app which needs to be automated somehow I'm pretty much novice user of TestComplete, and especially in WPF.

So, here's my problem:

I have one readOnly textBox1, with value that changes.
I also have one more ReadOnly textbox with value which is also value that changes.

How can I save both of those values (separated ofc) so I could use them later.

[what i want to create after - save that value from TextBox1 as value1, on TextBox2 save another value as value2, and after that substract value1 and value2. That result compare with some TextBox3 etc... ]

Help