A family of Microsoft relational database management systems designed for ease of use.
ArrayList is not part of VBA, so I assume you made a reference to the .NET System.Collections namespace, or you're using GetObject?
If so, and if all you're doing is storing data then you'd be MUCH better off using a standard VBA Array. While you can work with some of the .NET stuff in VBA, it's well known to cause issues (out of memory, for one), since all too often those .NET objects work with values that VBA and Access simply don't understand, and will try to convert.