There isn't a standard function to deal with DWY, but here's a bit of VBA that will do the job. It expects a 3 to 5 character string.
Put your DWY as a string 'dw[w]y[y]' in A1
A1 ='117' -- 2007
B1 =ConvertDWY(A1)
the second parameter is the length of the year section so if the year is more than 1 character
A1 ='1110' -- 2010
B1 =ConvertDWY(A1,2)
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Function ConvertDWY(ByVal varIn As String, Optional ByVal YearLen As Long = 1) As Date
Dim d, dd As Long
Dim m As Long
Dim w, ww As Long
Dim y As Long
Dim days As Long
Dim adddays As Long
Dim week As Long
Dim sDate As String
Dim SoY As Date
d = Left(varIn, 1)
y = 2000 + CLng(Right(varIn, YearLen))
w = Mid(varIn, 2, Len(varIn) - Len(d) - YearLen)
' get the whole number of days for the week value
week = (w - 1) * 7
sDate = "01/01/" & CStr(y)
' get the day 01/01 falls on
ww = (DatePart("w", sDate, vbSunday, vbFirstFullWeek) - 1) * -1
' get the first date of the year
SoY = DateAdd("d", ww, sDate)
' get the total number of days
days = week + d
' add the total number of days to the start date
ConvertDWY = DateAdd("d", (days + ww), SoY)
End Function
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The function returns a serial date so format B1 to a Date.
Edit: This is now working with the correct first day of the year.