Sorting 2 columns and a 10% reduction value to a separate column

Hi, In the attached sample I'm looking for a code that will sort column G with everything greater than 4, column F with everything greater than 400 and then add a value of '-10%' of each cell in column F to all the remaining cells in column Z.

Any help with this would be appreciated.

I've tried to do this using a macro but because the row items vary on a regular basis i cannot get it to work consistently.

Regards
John