Adding prefix to slot dimension

I'm trying to add the prefix '2X' to a slot dimension using the API. I have been able to add the text successfully but when I do the slot dimensions no longer update if the slot changes size. To fix the problem I can cut the text out of the PropertyManager and paste it back in. Has anyone successfully added a prefix to a slot dimension using the API?

Here is my code that updates the slot dimension;

Const strInc As String = "X "

Const strSlotCallout As String = " X "

Dim strDimensionTextCalloutAboveDefinition As String = swDisplayDimension.GetText(swDimensionTextParts_e.swDimensionTextCalloutAboveDefinition)

Dim strDimensionTextPrefixDefinition As String = swDisplayDimension.GetText(swDimensionTextParts_e.swDimensionTextPrefixDefinition)

If strDimensionTextCalloutAboveDefinition.Contains(strSlotCallout) Or strDimensionTextPrefixDefinition.Contains(strSlotCallout) Then

     intNumValue = Val(strDimensionTextPrefixDefinition)

     If intNumValue = 0 Then intNumValue = 1

     If strDimensionTextPrefixDefinition.Contains(strInc) Then strDimensionTextPrefixDefinition = strDimensionTextPrefixDefinition.Replace(Format(intNumValue) & strInc, "")

     intNumValue = intNumValue + x

     If strDimensionTextPrefixDefinition.Contains(strSlotCallout) Then

          strDimensionTextPrefixDefinition = strDimensionTextPrefixDefinition.Replace(strSlotCallout, "")

     End If

     If intNumValue > 1 Then

          swDisplayDimension.SetText(swDimensionTextParts_e.swDimensionTextPrefixDefinition, Format(intNumValue) & strInc & strDimensionTextPrefixDefinition & strSlotCallout)

     Else

          swDisplayDimension.SetText(swDimensionTextParts_e.swDimensionTextPrefixDefinition, strDimensionTextPrefixDefinition & strSlotCallout)

      End If

End If

SolidworksApi macros