What way can I display Scientific Notation under specific conditions?

[PixelPug]

I know how to change the Cell Format to Scientific Notation via Cell Format. However I have a list that has the number change based on the values entered in adjoining cell.

I want a whole number used for anything from 0 - 999,999. Everything over 999,999 I want displayed in Scientific Notation. While I can manually do this for anything over this value, I want it to change automatically if the cell value goes over 999,999.

[bebo021999]

Use Conditional formatting:

Choose the list range, i.e list range start from A1.
Menu data/ Conditional Formatting/Use a formula...
In Format values where...box, type this formula:
=A1>999999
Click on Format button, select Scientific, then OK

[MrShorty]

In addition to conditional format as bebo021999 describes, one can use limited conditions in custom number format codes (Guidelines for number format codes: https://support.office.com/en-us/art...2-09fab54be7f4 see the section about midway down titled "specify conditions"). I could see a code like "[<1e6]0;[>=1e6]0.0E+0"