Never say never...

1. Create a module with these functions:

  <Extension()> _
  Public Function GetIndex(ByVal items As ValueListItemsCollection, ByVal dataValue As Object) As Integer
    Dim result As Integer = -1
    Try
      If dataValue IsNot Nothing Then
        Dim i As Integer = 0
        For Each item As Infragistics.Win.ValueListItem In items
          If item.DataValue IsNot Nothing AndAlso dataValue.ToString.Equals(CStr(item.DataValue)) Then
            result = i
            Exit For
          End If
          i += 1
        Next
      End If
    Catch ex As Exception
      Throw New Exception(String.Format("{0}.GetIndex Error", items.GetType.Name), ex)
    End Try
    Return result
  End Function
  <Extension()> _
  Public Function GetItem(ByVal items As ValueListItemsCollection, ByVal dataValue As Object) As ValueListItem
    Dim result As ValueListItem = Nothing
    Try
      If dataValue IsNot Nothing Then
        For Each item As Infragistics.Win.ValueListItem In items
          If item.DataValue IsNot Nothing AndAlso dataValue.ToString.Equals(CStr(item.DataValue)) Then
            result = item
            Exit For
          End If
        Next
      End If
    Catch ex As Exception
      Throw New Exception(String.Format("{0}.GetItem Error", items.GetType.Name), ex)
    End Try
    Return result
  End Function
  <Extension()> _
  Public Function GetUIItem(ByVal ctrl As Infragistics.Win.UltraWinEditors.UltraOptionSet, _
                            ByVal dataValue As Object) As OptionSetOptionButtonUIElement
    Dim result As OptionSetOptionButtonUIElement = Nothing
    Try
      If dataValue Is Nothing Then Throw New ArgumentNullException("The data value may not be null")
      Dim item As ValueListItem = ctrl.Items.GetItem(dataValue)
      If item IsNot Nothing Then
        For Each childElement As UIElement In ctrl.UIElement.ChildElements
          If TypeOf childElement Is OptionSetEmbeddableUIElement Then
            Dim embeddableElement As OptionSetEmbeddableUIElement = CType(childElement, _
                                     OptionSetEmbeddableUIElement)
            For Each subElement As UIElement In embeddableElement.ChildElements
              If TypeOf subElement Is OptionSetOptionButtonUIElement Then
                Dim buttonElement As OptionSetOptionButtonUIElement = CType(subElement, _
                                     OptionSetOptionButtonUIElement)
                If buttonElement.Text = item.DisplayText Then
                  result = buttonElement
                  Exit For
                End If
              End If
            Next
            Exit For
          End If
        Next
      End If
    Catch ex As Exception
      Throw New Exception(String.Format("{0}.GetUIItem Error", ctrl.GetType.Name), ex)
    End Try
    Return result
  End Function
  <Extension()> _
  Public Function IsItemEnabled(ByVal ctrl As Infragistics.Win.UltraWinEditors.UltraOptionSet, _
                                ByVal dataValue As Object) As Boolean
    Dim result As Boolean = False
    Try
      If dataValue Is Nothing Then Throw New ArgumentNullException("The data value may not be null")
      Dim buttonElement As OptionSetOptionButtonUIElement = ctrl.GetUIItem(dataValue)
      If buttonElement IsNot Nothing Then
        result = buttonElement.Enabled
      End If
    Catch ex As Exception
      Throw New Exception(String.Format("{0}.IsItemEnabled Error", ctrl.GetType.Name), ex)
    End Try
    Return result
  End Function
  <Extension()> _
  Public Sub EnableItem(ByVal ctrl As Infragistics.Win.UltraWinEditors.UltraOptionSet, _
                        ByVal dataValue As Object, ByVal enabled As Boolean)
    Try
      If dataValue Is Nothing Then Throw New ArgumentNullException("The data value may not be null")
      Dim buttonElement As OptionSetOptionButtonUIElement = ctrl.GetUIItem(dataValue)
      If buttonElement IsNot Nothing Then
        buttonElement.Enabled = enabled
      End If
    Catch ex As Exception
      Throw New Exception(String.Format("{0}.EnableItem Error", ctrl.GetType.Name), ex)
    End Try
  End Sub

2. Add code like this to the ValueChanged event handler so that disabled items cannot be selected:

 Private Sub UltraOptionSet1_ValueChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) _
                  Handles UltraOptionSet1.ValueChanged
    If UltraOptionSet1.Value IsNot Nothing Then
       If UltraOptionSet1.IsItemEnabled(UltraOptionSet1.Value) Then
          UltraOptionSet1.Tag = UltraOptionSet1.Value ' Store the last valid selected value.
          ' Do something else if you need to.
       Else
          UltraOptionSet1.Value = UltraOptionSet1.Tag
          UltraOptionSet1.FocusedIndex = UltraOptionSet1.Items.GetIndex(UltraOptionSet1.Tag)
          UltraOptionSet1.Refresh()
       End If
     End If
   End If
End Sub

3. Enable or disable items like this:

UltraOptionSet1.EnableItem(5, False)

This example will disable the first option item with a data value of 5.

No, there is no way to disable individual items.

Is such an option available in infragistics 10.3 ?

Thanks.

-Matt

Please could put an example code to solve the above problem.

Thanks

When are you trying to execute this code?  You would likely need to do this in a CreationFilter because the elements could be repositioned several times throughout the course of the application, and doing this in AfterCreateChildElements will ensure that you actually do have elements to work with.

-Matt