Forms Data Controls :: Validation For Checkboxlist Inside Listview

I'm trying to do a validation for checkboxlist on a server side as all java approaches didn't work. However, probably due to the checklistbox is inside a listview the FindControl is empty. how to find a control inside a listview on a button click event when the button is outside of the listview.

<asp:CustomValidator
ID="rfchblAnswers"
runat="server"
ErrorMessage="* Please, select at least a one checkbox."
OnServerValidate="cblCustomValidator"
EnableClientScript="false"
ValidationGroup="EnterData"
Display=
"Dynamic" />
Public
Sub cblCustomValidator(ByVal objSource
As Object,
ByVal objArgs As ServerValidateEventArgs)
Dim chblAnswers As CheckBoxList = _
CType(lv_qstns.FindControl("chblAnswers"), CheckBoxList)
If CType(lv_qstns.FindControl("chblAnswers"), CheckBoxList)
IsNot Nothing
Then 'it's not working here as it cannot find the control inside a listview
Dim boolFlag As
Boolean = False
For Each li
As ListItem In chblAnswers.Items
If li.Selected Then
boolFlag = True
End If
Next
If boolFlag Then
objArgs.IsValid = True
Else
objArgs.IsValid = False
End If
End If
End Sub