When I have a lot of data that I want to use the "convert to Number", the
pop-up with the "exclamation mark inside the yellow diamond" disappears.

Essentially, I want to highlight 1 column, but 5 screens worth of data,
using SHIFT-PAGEDOWN. However, when I go past one screen, the yellow diamond
does not consistenly appears. I need this so that I can use the "convert to
number" functionality".

Any ideas on how to make this appear, or is there another way to "convert to
number"?

Thanks for any ideas!