WXR import XML without post IDs

Hi.

It happens that someone sends me a csv with a bounch of data that I must convert to WXR format and then import into the blog.

It happens, also, that I have to hardcode an offset ID to start importing from, into xml, so that imported posts will be imported with IDs greaters than that ID.

I wonder if I could avoid setting this offset-starting-ID, and let it pick by mysql/import function as it happens when they are written in the dashboard.