Cells(i, 15) = Application.WorksheetFuction.SumIf(Sheets("Фактические начисления").Range("Q:Q"), _
              Sheets("Расчет").Cells(i, 3).Value, Sheets("Фактические начисления").Range("AJ:AJ"))

Option Explicit

Sub tt()
Dim a, b, i&

With Worksheets("Данные для расчета")
a = .UsedRange.Columns(15).Value
b = .UsedRange.Columns(33).Value
End With

With CreateObject("Scripting.Dictionary")
For i = 2 To UBound(a)
.Item(a(i, 1)) = .Item(a(i, 1)) + b(i, 1)
Next

With Worksheets("расчет")
a = .UsedRange.Columns(3).Value
b = .UsedRange.Columns(15).Value
End With

For i = 2 To UBound(a)
b(i, 1) = .Item(a(i, 1))
Next

Worksheets("расчет").UsedRange.Columns(15).Value = b
End With

End Sub