I presume that LSeries can be any value or is it as per your example limited to 999?

But why a nested cursor!

One cursor to get distinct LSeries and do a set based update to update target table. Unfortunately this would involve using dynamic sql ( yes I know to be avoided at all costs but... )

if the LSeries is limited to 999 say then create 999 procs to do each table update and then one cursor to get distinct LSeries and EXEC the relevant proc

to do similar to above with cursor you could put distinct LSeries into temp table, select top one, do update, delete the one selected and loop back round until no rows left