Potrzebuje pomocy z makrem macierzy , co robi a(l, j) = (a(l, j) - ar2 * a(i, j)) ? : )
Dim n, i, j, l, ar1, ar2 As Double
Dim a(), w As Double
n = Range("c13").Value
ReDim a(n, n)

For i = 1 To n

For j = 1 To n
a(i, j) = Cells(2 + i, 1 + j)

Next j
Next i

w = 1

For i = 1 To n
ar1 = a(i, i)
If ar1 = 0 Then
MsgBox "Nie, przez 0"
GoTo koniec
End If

For j = 1 To n
a(i, j) = (a(i, j) / ar1)
Next j

For l = i + 1 To n
ar2 = a(l, i)
For j = i To n
a(l, j) = (a(l, j) - ar2 * a(i, j))
Next j
Next l
w = w * ar1
Next i
koniec:

If ar1 > 0 Then
Range("k13").Value = w
End If

End Sub