Date Must Be Between 1900 and 2100

[D.E.L.B.]

Okay so basically my program is a program that validates dates in this format:
DD/MM/YYYY

However, I need I guess some sort of statement (my brain is thinking an IF ELSE) to make sure that the user does not enter a date that is less than 1900 and not greater than 2100; or in other words: it must be between 1900 and 2100.

I don't suppose anyone could help me? The code I have done so far is here:

    Private Sub btnCheck_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCheck.Click
        Dim dateString, format As String
        Dim result As Date
        Dim IsValid As Boolean = False
        dateString = txtDate.Text
        format = "dd/M/yyyy"

        If format <  Then
            IsValid = False
        End If

        Try
            result = Date.ParseExact(dateString, format, System.Globalization.CultureInfo.InvariantCulture)
            IsValid = True
        Catch
            IsValid = False
        End Try
            If (IsValid) Then
                MessageBox.Show("Valid.")
            Else
                MessageBox.Show("Invalid.")
            End If
    End Sub

The validation works but the assurance of the year doesn't work.

Thanks.