is this how to work out how we will be affected

pamelab21

I earn 10250 pa and other half is on 22k pa. We are planning for a 2nd child but also to move home, I am not relying on benefits in any way but at the moment if we calculate childcare for 2 kids for 1 week it would be £150 pr week (1st child will get 12.5 hrs paid per week after she is 3).
The entitled to website and the hrmc website both say we would get £97 per week child tax credit which will help pay the childcare, however after the changes due in 2012 should I deduct an extra 0.02p for every extra £ we earn over the £16k threshold to work out what will be deducted from the £97 per week?
Is that how it works or have I got it all wrong?