I saw no solution, even with your hint about the nature of the move. 
 
Then I let check Fritz, also no solution. 
It suggests Ncb5, after cxb5 it sees no advantage. 
 
Puzzled :-)

Bxc7!

Bennie, try making a few moves after Ncb5. The position is lost for Black

http://pogonina.com

Hello. I tried after Ncb5, but I'm not sure they are right. 
 
1.Ncb5 axb5 
2.Qa5 Kb8 (2...b6 or 2...Bd6 3.Qa8#) 
3.Qxc7+ Ka8(or Ka7) 
4.Qa5# 
 
1.Ncb5 cxb5 
2.Qf3 c6 
3.Qa5 b6 
4.Qxa6# 
 
1.Ncb5 cxb5 
2.Qf3 Bc6 
3.Nxc6 bxc6 (3...Bd6 3...Re 
4.Qxc6 Kb8(4...Bd6 5.Bxd6 Kb8 6.Qxc7+ Ka8 7.Qxd8+ Kb7 8.Qc7+ Ka8 9.Qb8#) 
5.Qxc7+ Ka8 
6.Qxd8+ Kb7(or Ka7) 
7.Qc7+ Ka8 
8.Qb8# 
 
3...Bd6 
4.Bxd6 cxd6 (4...bxc6 5.Qxc6) 
5.Ne7+(forking K and Q) 
 
3...Re8 
4.Qa5 b6(4...bxc6 5.Qxc7#) 
5.Qxa6# 
 
1.Ncb5 Bh6 
2.Na7+ Kb8 
3.Nxc6+ bxc6(3...Ka8 4.Qxd8#) 
4.Qxd8+ Kxa7 
5.Qxc7+ Ka8 
6.Qb8#

http://chesski.blogspot.com/

> Bennie, try making a few moves after 
> Ncb5. The position is lost for Black  
 
Thx for your reply 
 
Natalie I could not find anything, maybe I overlooked something.. 
 
Suppose black plays 1. cxb5 
Then what should white do ?  
2. Dc3 perhaps, but that is not winning: 
 
2.Bd5 
3.Bxd6 Bc6 
(4.Nxc6 Rxd6) 
 
and it looks equal. 
 
Still puzzeld, sorry

1.Ncb5!! 
A)1...axb5 2.Qa5! and Black gets mated either in one way or another. 
B)1...Bd6 2.Nxd6+ and White wins a pawn 
C)1..cxd5 2.Qc3!! c6 3.Qa5! or 2...Bd6 3.Bxd6 c6 4.Qa5! and Black will die without a Bishop !