How to prevent the same record from being updated at the same time

[matsui]

I found Simultaneous Update Alert script my instance：

// Warn when two users are editing the same record
function onSubmit() {
var updatedOn = gel('onLoad_sys_updated_on').value;
if (!updatedOn)
return;

var gr = new GlideRecord(g_form.getTableName());
if (!gr.get(g_form.getUniqueValue()))
return;

var dbUpdatedOn = gr.sys_updated_on + '';
var dbUpdatedBy = gr.sys_updated_by + '';
if (updatedOn != dbUpdatedOn)
return confirm(new GwtMessage().getMessage("{0} updated this record since you opened it - overwrite with your changes? Additional comments and Work notes will not be overwritten.", dbUpdatedBy));
}

Based the above, it will submit, when user select yes in confirm message.
I don't want to submit, so I changed this script like the following, but it did not worked.
Even if I pushed update button, it didn't happen anything. In other word, I can't save the record.

// Warn when two users are editing the same record
function onSubmit() {
var updatedOn = gel('onLoad_sys_updated_on').value;
if (!updatedOn)
return;

var gr = new GlideRecord(g_form.getTableName());
if (!gr.get(g_form.getUniqueValue()))
return;

var dbUpdatedOn = gr.sys_updated_on + '';
var dbUpdatedBy = gr.sys_updated_by + '';
if (updatedOn != dbUpdatedOn)
confirm(new GwtMessage().getMessage("{0} updated this record since you opened it - overwrite with your changes? Additional comments and Work notes will not be overwritten.", dbUpdatedBy));
return false;
}

What should I do for it?

[Sandeep Rajput]

@matsui 

return false;

In the last line of your script is not letting the form submit. Remove this line and the form will start submitting.

[matsui]

@Sandeep Rajput 

My explanation was not enough.
When this script is run, I will not be able to submit in all cases (even if I am the only one who has opened the record).
Also,confirm message did not show. I could not understand that reason.