game engine - How to check if no condition was met? -

<check object "if there not object @ (x,y)"> { <create instance "create instance of object @ (x,y)"> }  ... 

using game maker events, created repeated process 1 above, checking 1 space , other, , filling empty ones. code works fine, want add message @ end if none of spaces empty. tried using else @ end, uses last if. sorry bad wording, can elaborate if needed.

what want if-else if-else structure. can nesting conditions:

if () {     ... } else {     if(...) {        ...     } else {         if(...) {            ...         } else {            ...         }     }  } 

though code easier read use gml, rather visual language, in gml can this:

if () {     ... } else if(...) {     ... } else if(...) {     ... } else {     ... }