Extract data from a long text field

Yes, I can make an IF statement, but how will the IF know which to use.  Dan's post on an excel forum looks like it may have been from you or one of your staff and it had the same fundamental problem.  how to know if we should use the right side digits or the left side digits and this is complicated by the fact that the item description may have digits in it which are not the case qty, but refer to the size of the item in oz or in ML.