How to prevent user launch same form multiple times in Oracle application in the same login

Our user sometimes lauched same forms in Oracle application again and again, create many sessions and sometimes the changes on the same form lock each other. Is there anyway to prevent user launch same form multiple times in Oracle application in the same login?

Thanks!

Following is our system enviroment

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Database Server
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RDBMS : 11.2.0.3.0
Oracle Applications : 12.1.3
Machine : mmrsdev3
User : APPS
Oracle SID : MMIDV1
System Date : 26-NOV-2013 16:45:39
Database Server PID : 43713652
Session SID : 593
SERIAL# : 1327
AUDSID : 11679033
Database CPU Usage (in secs) : 2514.14

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Forms Server
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Oracle Forms Version : 10.1.2.3.0
Application Object Library : 12.0.0