Необходимо вычислить сумму элементов четных строк матрицы MxN - VB

Sub myProg()
 
Dim i As Integer, j As Integer, n As Integer, m As Integer
Dim sum As Integer, mas
 
NAX:
  m = InputBox("Vvedite razmer matricy m:")
If m <= 0 Then GoTo NAX
 
NEX:
  n = InputBox("Vvedite razmer matricy n:")
If n <= 0 Then GoTo NEX
 
ReDim mas(1 To m, 1 To n) As Integer
 
For i = 1 To m
  For j = 1 To n
    mas(i, j) = InputBox("Vvedite elementy matricy: [" & i & "," & j & "]:")
  Next j
Next i
 
sum = 0
For i = 1 To m
  If (i Mod 2) = 0 Then
    For j = 1 To n
       sum = sum + mas(i, j)
    Next j
  End If
Next i
MsgBox "Summa elementov chetnyh strok matricy:" & sum
 
End Sub