google apps script lock service

// BEGIN - start lock here

var lock = LockService.getScriptLock();
try {
    lock.waitLock(30000); // wait 30 seconds for others' use of the code section and lock to stop and then proceed
} catch (e) {
    Logger.log('Could not obtain lock after 30 seconds.');
    return HtmlService.createHtmlOutput("<b> Server Busy please try after some time <p>")
    // In case this a server side code called asynchronously you return a error code and display the appropriate message on the client side
    return "Error: Server busy try again later... Sorry :("
}
// note:  if return is run in the catch block above the following will not run as the function will be exited

//  Do lots of stuff - ie apply dynamic background colors based on previous entries colors, define the target range and set values, set data validations  

lock.releaseLock();

// END - end lock here