vb.net need to convert string to integer

Question

In a vb.net 2012 application I have the following code that works:
Protected _schoolyear As Integer
Protected _schoolyearcheck As String
If (IsDBNull(_schoolyearcheck)) Or (Not IsNumeric(_schoolyearcheck)) Or CInt(_schoolyearcheck < 2000) Or (CInt(_schoolyearcheck) = _schoolyear) Then
_schoolyear = _schoolyear
ElseIf CInt(_schoolyearcheck) + 1 = _schoolyear Then
_schoolyear = CInt(_schoolyearcheck)

End If

However I am wondering about the _schoolyearcheck field. I have a funciton call to the sql server database that really returns an integer value. However I
am concerned that the call may return a null or something that is not numeric. That is why I am using a string value. Due to that fact I am converting the
string to an interger in the the code Above. Thus can you show me code that would be better to use than converting all the values listed above?