Word Problem 4 - Horses in the field part 2

There are 33 horses in a field. 15 horses go into the barn. Then 7 of them come back out. How many horses are standing in the field?
Write a program in Visual Basic to find out how many horses are standing in the field.
Gather the initial value in a text box.

   Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click  

     'Declare variables  

     Dim I, O, B, horses As Integer  

     'Set values  

     O = 15  

     I = txtInitial.Text  

     B = 7  

     horses = I - O + B  

     'Display results  

     MessageBox.Show("There are " & horses & " horses in the field.")  

   End Sub  

 End Class