Something like this...

For r = 5 To NumBins
Range(r, 2).Select
Range(Selection, Selection.End(xlDown)).Select
RangeName = "rngCol" & r
RowName = "'Wfr Lvl'!R1C" & r
ColName = "'Wfr Lvl'!C" & r
' ActiveWorkbook.Names.Add Name:=RangeName, RefersToR1C1:= _
"=OFFSET(RowName,1,0,COUNTA(ColName)-1,1)"
Next r