Validating checkbox list in Gridview

Code: 
 
  Protected Sub CustomValidator_Checkboxlist_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs)
        Dim i As Integer
        Dim selected As String
        
        
        
        Dim gvRow As GridViewRow
        Dim iCounter As Integer
        
        
        For Each gvRow In GridView_Consol_HBL.Rows
            If iCounter = -1 Then
                iCounter = 0
            End If
            Dim cbxList As CheckBoxList = GridView_Consol_HBL.Rows(iCounter).FindControl("CheckBoxList_Consol_Docs")
           
            For i = 0 To cbxList.Items.Count - 1
                If cbxList.Items(i).Selected Then
                    selected = "yes"
                   
                End If
            Next
 
            iCounter += 1
 
    
        Next
        
        
        If selected = "yes" Then
                
            args.IsValid = True     
 Else
            args.IsValid = False
        End If
        
        selected = ""
            
        
    End Sub