iTunes Sync Backup Query

Hello All. Was wondering if anyone could help me with this

When I sync my iphone with Itunes on my PC via the USB cable the backup runs first as expected. The sync completes fine and the last backup date is displayed all correctly. If I then leave my iphone connected to my PC via USB as I often do and then sync again it does not run the backup and skips this stage. Thing is I may use my ihpone while it is connected. Maybe recieve a txt or input a calendar event. There is then something to backup so I would therefore expect the iphone to backup again with a sync. So if i run a sync i want it to backup every time no matter what. Im sure it used to backup everytime I ran sync. But now it seems it only does the first time it is connected to my PC. Yes I can click on manual backup and it forces a backup fine but I want it to backup with every time I click sync.

My aim here is to sync my phone when first connected then be able to sync at any further point such as when i am about to leave with my phone and know that further backups are all completed.

Any help would be great and im sure someone will have a simple answer for me so thanks in advance.

AutumnLights