Struggling with if...then and logical operator

[Inferrd]

I think it is easier on the brain if you break it down further, so you are not mentally doing multiple comparisons every time you write an If clause.

Example using a Button and two TextBoxes:

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim a, b As Integer
    Integer.TryParse(TextBox1.Text, a)
    Integer.TryParse(TextBox2.Text, b)
 
    Dim oneIsSmall As Boolean = (a < 0 OrElse b < 0)
    Dim oneIsBig As Boolean = (a > 1000 OrElse b > 1000)
 
    If oneIsSmall AndAlso oneIsBig Then
        MessageBox.Show(String.Format("one is too small and one is too big : {0}, {1}", a, b))
    ElseIf oneIsSmall Then
        MessageBox.Show(String.Format("one or both are too small : {0}, {1}", a, b))
    ElseIf oneIsBig Then
        MessageBox.Show(String.Format("one or both are too big : {0}, {1}", a, b))
    Else
        MessageBox.Show(String.Format("both are within range : {0}, {1}", a, b))
    End If
 
End Sub