Percentile/IF/empty cells

I'm currently working with excel, trying to get back the top scoring returns from shares traded on a stock index. Since this index has changed a lot over time, I put all shares on the same sheet, named the rows by date and the columns by shares. What I need to do is get excel to return values that lie within a certain percentile on a new sheet. I do this by using the following formula:

=IF('Monthly performance'!D24>=PERCENTILE.EXC('Monthly performance'!$B$24:$MB$24;0.7);'Monthly performance'!D24;"")

This works well as long as all the values in a row are directly next to one another, but if a few cells are blank, excel counts these cells as if they are zero skewing the percentile distribution. In the sheet from where I get the data (where the blanks exist) I use an Iferror formula that gives "" Iferror. that may be the problem. Although I have tried to copy paste values (so the blanks really are blanks) but the percentile function still gets skewed.

Please see attached.Momentum Excelhelp.xlsx

Thanks for helping me out!

Sorry guys, I've got 2010.

However, the problem still remains when using only PERCENTILE

You guys got some ideas then?