I know it can be done, but I just don't know the syntax.

I want to tell Excel, to check if a range of cells in the a row as a
particular formating, and for each cell with that formatting to make the some
of the numbers in those cell.

I started the programming, but I just don't know how to write the "Then"
part (in cell E15, make the some of all the cell with the matching formating)

Sub test1()
If Feuil59.Range("U15", "AT15").Interior.ColorIndex = 50 Then
E15 = Sum(U15, AT15) ?????
End If
End Sub

Hope I'm clear enough and thanks for your help

Sophie