Calculation program

[imbored]

i am trying to make a program that starts off with 3 buttons or a drop box. when one of them is selected, it would turn into a different layout and have many text boxes that the user have to input numbers into and the program calculates according to the numbers the answer.

1st
The user inputs numbers into boxes like 5,6,7
according to the thing chosen in drop box the program calculates the answer and outputs it in another box near the bottom


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i need help, how do you get from the 1st form to a different new page with different layout. Also how do you make sure that only integers are allowed to be inputted into the boxes in the 2nd page. or at least a verification so that the program won't have any errors if alphabets are inputted. im not skilled with visual basic. i am just trying ot make a simple program for fun this is not school work. just want to make a simple calculator for a game. if you have any guides or tutorial that might help please link me.