Unfortunately I don't think any of the online personal finance applications will do what you're asking.
Most (if not all) online person finance software uses a combination of partnerships with the banks themselves and "screen scraping" to import your data. This simplifies things for the user but is typically limited to whenever the service was activated.
Online personal finance software is still relatively young and doesn't offer the depth available in a desktop application (yet). If you are unwilling to part with historical data you spent years accumulating you are better off with a desktop application.
Online Personal Finance Software
- Available from any computer with a web browser
- Automatic imports from supported banks
- Easy to use
- Feature limited
- Service disruptions
- A number have folded forcing their users to start over somewhere else
Desktop Personal Finance Software
- More mature
- Deeper analysis tools
- Can be used offline
- Data can only be accessed from computer where software is installed
- Steeper learning curve
In my humble opinion the personal finance software industry really needs a hybrid approach. A desktop application that is synchronized with a website. Offering the stability and tools of a desktop application with the availability of a web application.