Trying to update GUI(Textbox) using another file in Vb.NET

Question

Hello There,

I have created Main Form and I want to update my results in the main Form using different file. The result box is in Tabcontrol. 

Here is my code I am trying to use but its not updating the results 

Form1.Textbox1.Text = Number

Can someone please help me with this? Please let me know if you have any questions. 

Thank you for your help.

Jatin