Option Explicit
Sub TEST()
Dim Brr, Crr(1 To 1000), Drr(1 To 1000), D, i&, M%, N%, xR As Range, Ra As Range
Set Brr = Range([H2], [B65536].End(3)(1, 3))
For i = 1 To Brr.Rows.Count
M = Brr(i, 2).MergeArea.Count
N = N + 1
Crr(N) = M
i = i + M - 1
Next
Set xR = Brr(1)
For i = 1 To N
For Each Ra In xR.Resize(Crr(i), Brr.Columns.Count)
Drr(i) = Drr(i) + (Val(Ra.MergeArea(1)) / Ra.MergeArea.Count)
Next
If Drr(i) <> 0 Then xR(1, 8) = Drr(i)
xR(1, 8).Resize(Crr(i)).Merge
Set xR = xR(Crr(i) + 1)
Next
xR(1, 8) = "=SUM($K$2:K" & Brr.Rows.Count + 1 & ")"
End Sub