Sorting Algorithm

I need a database solution that is custom made which must be able to easily handle 100Giga bytes of data and 25 million records or more .
The specification is as follows:
> > 1. Accept a large alpha-numeric key of no less than 255 characters.
> > 2. Associate that key with any DOUBLE size record number I give it.
> > 3. If I search/continue searching that key-it must give me the next
> > record
> > number until finally a "last record number" flag is set.
> > 4. If I search for a given record number it will give me all
> > associated keys.
> > 5. I can delete any key/record combination quickly.
> > 6. It must be fast/efficient/bug free and written entirely in Visual
> > Basic 5
> > without classes.
> > 7. I must have simple access to the SORTED LIST portion of the child
> > leaf/nodes. In other words I'v read that in some tree's the child
> > portion
> > is automatically sorted.
i am trying out the algorithms of binary tree ,binary TRIE and RED-BLACK binary TRIE.i am not clear which of these algorithms fit for this problem efficiently.
hope if any one can suggest me a solution for this problem.
thanking you.
regards
nag