TAGau

You can use this Epoch Event by adding an entry to your epochconfig.hpp events config:  https://github.com/EpochModTeam/Epoch/blob/release/Server_Install_Pack/%40epochhive/epochconfig.hpp#L14-L20

For MessageServer Event just add this line: (1800 is the number of seconds between runs.)
{ 1800, "MessageServer" },  

Here is a modified version which should do  what you want:
https://gitlab.com/themgm/Arma_3_Misc/raw/master/Ring_of_ProtectionPlus/Ring_of_ProtectionPlus.sqf
 
no arma here so I haven't tested it - let me know if it doesn't work...