Replace string with vba

I have strings which vary like:

1. 12 X 14 SCALE PAPER 21#(5 X1M/CS) 9927

2. 12 X 18 DRY WAX21LB (1M/BOX)


3. 12 X 14 DRY WAX SCALE 18LB (1M/BDL/5 BDL/CS) J


I have to do maths on these which will be like this:

1. 12*14*21
2. 12*18*21
3. 12*14*18

I am having a hard time using REPLACE/SUBSTITUTE to solve this, because the spaces vary between different cells.

Suggestions?