|So let me see if I understand this...|
You have a such a complex sheet that splitting these multi-line cells into individual cells so that standard date operations can be performed on them will cause "too much" other problems, so instead you want a "simple" solution for extracting text based dates from longer text strings which can be turned into dates so that mathematical operations can be performed on them. Have I got that right?
OK, is this what you would consider simple?
1 18-Nov-2010, 21-Nov-2010,
This formula will return 2, since 14-Nov-2010 - 12-Nov-2010 equals 2.
I'll leave it to you to figure out a "simple" solution for any other date analysis on these cells.
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