You're getting runtime error 91 because it didn't find "SD-1" and your code assumes it always will.
dataobj.Range(Cells(1, 1), Cells(1, c)).Find("SD-1", LookIn:=xlFormulas, LookAt:=xlWhole).Activate
If you change that to the following, it may still not find "SD-1", but it shouldn't give you error 91.
Dim rFindThis As Range
Set rFindThis = dataobj.Range(Cells(1, 1), Cells(1, c)).Find("SD-1", LookIn:=xlFormulas, LookAt:=xlWhole)
If Not rFindThis Is Nothing Then rFindThis.Activate
You may need to post an example workbook in order to determine why the value is not found.