Compile Error: User-defined type not defined

Error Message

When running VBA code within ArcMap or ArcCatalog that includes references to Network Analyst objects, you get the following error message when you attempt to run the code:
'Compile error: User-defined type not defined'

Cause

esriNetworkAnalyst.olb and esriNetworkAnalystUI.olb are not included in the VBA list of references.

Solution or Workaround

1. Within VBA, click on Tools > References to show the References dialog box.
2. Check on the references 'ESRI Network Analyst Object Library' and 'ESRI NetworkAnalystUI Object Library'.
3. Click OK to dismiss the dialog.
4. Re-run the VBA code.