Just to clarify: Do you mean a generator that basically continues rolling on the
treasure table at the user's requested LEVEL until it gets to an amount roughly equal to the user's requested GP_VALUE?
In your example, that would mean the generator rolls on the "1st level" sub-table until it has a total treasure of around 2000gp. Is that right?
I've never seen a generator like that. The closest I've come across online is the
treasure generator at donjon, which can combine several treasure parcels of the same level into a single hoard. To come kind of close to what you want, maybe you could figure out how many "treasure parcels" are in your desired GP_VALUE, and request that many "hoards" at donjon.
For instance, using your example of 2000gp of 1st level treasure:
1) Look up value of 1st level parcel on SRD table "
treasure per encounter": a 1st level parcel averages 300gp.
2) So the desired value 2000gp/300gp is about 7 1st level parcels.
3) At the donjon generator site, create 7 level 1 hoards, being sure to tick the "Combine?" option at the bottom.
Problem is that this will almost never be "about 2000gp". My quick test run of 10 attempts gave a low of 600gp, high of 1600gp, average around 1100gp.
This way is also not very automated

Maybe there's something better for this task out there....