Hi all.
First of all I am a beginner and I am sure there are better ways to do every piece of my macro below.
Please see and let me know if you have any suggestions to make it work faster.

Many thanks for your time.

Sub Macro2()
Cells(4, 22) = Cells(4, 1)
Cells(4, 23) = Cells(4, 2)
i = 5
j = 4
Do While Cells(i, 1) = Cells(j, 22) And Cells(i, 2) = Cells(j, 23)
If Cells(i, 19) > Cells(i, 18) Then
Cells(j, 24).Value = "C"
Do While Cells(i, 1) = Cells(j, 22) And Cells(i, 2) = Cells(j, 23)
i = i + 1
Cells(2, 27) = i
Cells(3, 27) = j
Loop
If IsEmpty(Cells(i, 1)) Then
GoTo d:
End If
j = j + 1
Cells(2, 27) = i
Cells(3, 27) = j
Cells(j, 22) = Cells(i, 1)
Cells(j, 23) = Cells(i, 2)
Else:
i = i + 1
Cells(2, 27) = i
Cells(3, 27) = j
If IsEmpty(Cells(i, 1)) Then
GoTo d:
End If
If Cells(i, 1) <> Cells(j, 22) Or Cells(i, 2) <> Cells(j, 23) Then
Cells(j, 24).Value = "UNC"
j = j + 1
Cells(j, 22) = Cells(i, 1)
Cells(j, 23) = Cells(i, 2)
End If
End If
Loop
d:
End Sub