Atomic transactions between .NET and COM (Interop) connections

Hello,

I am developing my .NET application using two tecnologies, .NET and COM
(called by Interop).

Let's imagine this situation:
1. I insert/modify a register (A) from my .Net app.
2. After, I call (using interop) a VB6 process which inserts/updates another
register (B) which is relationated with A (so, at the first step I executed a
COMMIT)
3. If step 2 not finish successfully, I can rollback the operation made with
B; but my QUESTION is: how could I rollback the operation made with register
A from my .Net applicacion?


Because of my application features, I am limited enough; my aplpication is:
a) Multi-User --> so I cannot use transaction isolation level "Read
Uncommited".
b) Multi-DB --> so I cannot use COM+ (i.e. Oracle is not implemented with COM)

Could anybody help me, please? Very thanks in advance.

Montse