I use the MsiGetProperty function to obtain the value of IS_SQLSERVER_SERVER throughout my installscript project. By way of MessageBox I see that the value is correct all the way though OnFirstUIBefore and OnMoving.
I notice in OnFirstUIAfter the value no longer has any data! Why is this? If I look in the msi verbose log file I see that IS_SQLSERVER_SERVER has a value right through so I am not sure why at OnFirstUIAfter it is no longer populated.
That event might occur during deferred mode, in which case you'll need to go through CustomActionData to get a property's value; searching the KB and these forums for "CustomActionData" will return some techniques you can use.
