runtime error '40041'

i am using Sheridan as grid to my form. In SSDBgrid properties i have named every columns. When i want to read row by row, this error message come out. Below is the code:

Private Function CreateLNAndInd()
      Dim intNumRow As Integer
      Dim Ln As Integer
      Ln = 1
      With mclsGrid1
         .MoveFirst
         Do While Not .EOF
            .rdoColumns("WCYC_LN").Value = Ln
            .rdoColumns("WCYC_IND").Value = "*"  
         Ln = Ln + 1
         .MoveNext
         Loop
      End With
End Function


Actually there have few more columns.

Does anyone know this problem??? pls anwer me.