title: How to add only numerical values to text boxes in vb.net
body: <p>I have made a vb.net form that has 3 text boxes and a button called Calculate. All I want to do is enter some values to the textboxes and click the button which calculates the numbers. I have done the calculation coding part.</p>
  
  <p>Now I want to enter only numbers to the textboxes and if I enter alphabetics or symbols I need to get an critical error message with ok button when I click the ok button.</p>
  
  <p>How can I do this? </p>