[VB 2010] How to store user input using functions, multiple forms and exporting to Excel or a graph type output.

Hello r/learnprogramming! FYI: all of the variables are stored inside a modal, I have two functions one that does a simple FV return and another that does a If then else, For, Loop, These are based on the users input (some basic math) and stored, (this is the Function in question) The functions work once on one form but will not work on another form.

I am trying to carry over user input from form to form or store the input into a file to recall for later use in the program. I have used a function to create some of the output it works but only for one value, inside this function i have four other values I want to return to the respective form for display to the user. How it would be possible to extract the value that the function has created storing it for output for future use in another form? How can I "do math" (+,-,*,/ ect..) on inputs from form to form. IE frmmain.txtInput.text - frmSecond.txtOtherInput.text? I have tried to convert these variables using string and double. Sadly, I have been unable to display the result in another form. Finally, what command would i use to export this to an excel worksheet and or a text file?

I am pretty new to programming in general ANY suggestions or HELP is greatly appreciated. Thank You.