Dim A() As Integer
Dim i As Integer
Dim j As Integer

ReDim A(2, 2)

A(0, 0) = 1
A(0, 1) = 2
A(0, 2) = -3
A(1, 0) = 4
A(1, 1) = -5
A(1, 2) = 6
A(2, 0) = -7
A(2, 1) = 8
A(2, 2) = 9

For i = 0 To 2
    For j = 0 To 2
        If A(i, j) < 0 Then
            A(i, j) = 0
        End If
        Debug.Print A(i, j)
    Next
Next