QTP中读取EXCEL表中的列数

public Function getColumns(filename,sheetname)
Dim wb,bs
   Set wb=createobject("EXCEL.Application")
   Set bs=wb.workbooks.open(filename)
   bs.worksheets(sheetname).activate
 i=1
   Do while(bs.worksheets(sheetname).cells(1,i).value<>"end")
  i=i+1
 Loop
 getColumns=i-1
bs.close
 wb.workbooks.close
End Function