You can set your preferences by going to Tools/options/spelling and then you'll find some checkboxes and select the ones you want to ignore.
The menu looks like this:
For more information on these options and others, please visit the TeXnic Center's options documentation
However, please bear in mind that ---as stated in the documentation---, the argument of the command is always spell-checked, and not the command itself.
Furthermore, if you wish to include this feature for specific commands (such as
\ref) in future TeXnicCenter versions, please add your recommendation in the TeXnicCenter Feature Request Page
Nevertheless, there is kind of a workaround: as you can see in the picture attached, you can ignore things with numbers and/or uppercase... so you can always use numbers and/or uppercase for the arguments of