Convert dynamic content to static in Numbers
Select and copy the source cells, then hit ⇧⌘V, which is the default shortcut for the Edit » Paste Formula Results menu command.

(I assume that by dynamic value, you are referring to the the result of the calculation of an entire formula and not to the individual cell references you are using as part of the formula’s expression. Feel free to update and clarify your question if you disagree.)



If you want the static results to persist in your original cells as well, just hit ⌘C ⇧⌘V to paste the results in place.