The simple answer is no.
The longer answer is that custom fields is a feature that is being considered (worked on) for a future revision/version. Note that this does not mean that the field could be used in the way you're describing.
Alternatively, one way that you could tackle this without requiring anything custom would be to make use of the categories system.
Simply create a sub-category called "Asset", and populate the selections with all your assets. Then when creating an event, you'll be able to select the asset. Then from the asset page, you can use the $showCat variable to limit the display of events to only ones that have that asset selected. This will work well if you only assign a single asset per event.
In the case where multiple assets could be selected, then you would have to create a sub-category for each asset, and have a single selection for each. The selection could be "Yes" or "Reserved" or "Assigned", etc... Then from the asset page, you'd use the same technique as above.
EPC Tutorials... We're here to help!
Offering custom integration services. Contact me here
* Not affiliated with EasyPHPCalendar or NashTech Inc.