Bootstrapping-Random sampling with replacement

On sheet '40%' of the attachment I want to place a macro trigger button. This trigger would action the following:
1/ Sort all the data rows in a random order (apart from rows 1 & 2 )
2/ Count the number of randomly sorted rows and calculate 60% of the row count. In the attachment it would be 60% of 28 rows = 17 rows (rounded)
3/ Copy the first 17 rows and paste into Sheet1
4/End of macro.

Now I can record this but have come up with two problems that my limited knowledge of vba can't solve?
1/The total number of rows on the '40%' worksheet varies, so the reference needs to be dynamic.
2/ I've had no success in randomly mixing up the data with a trigger.

The concept is to take a set of historical data, take a 60% sample of it all mixed up and not in time order, this sample then goes to a pivot table for further analysis, but along with other runs of the same sampling, to generate an unbiased total sample, for analysis going forward.

Cheers and Happy Holidays to all.

This will do:

Code:

---

Sub M_snb()
  With Sheet1.Cells(1).CurrentRegion
      sn = .Offset(2).Resize(.Rows.Count - 2)
    End With
 
  With Sheet1.Cells(1, 50).Resize(UBound(sn))
      .Value = "=rand()"
      Sheet2.Cells(30, 1).Resize(Round(UBound(sn) * 0.6, 0), UBound(sn, 2)) = Application.Index(sn, Application.Rank(.Offset, .Offset), [transpose(row(1:20))])
    End With
End Sub

---

NB. Delete column U in sheet "40%" first.

Wow, great work snb! Just a few lines of code and you'll save me so much time. Thankyou so much.:hi:

I hope you'll analyse the code so you can explain to any other what every element does.