When we deploy a form in our development environment, our compile script creates a txt output file. This enables us to search these files. If you have someone on your staff that is familiar enough with Java, you could use the JDAPI utility to search all of your forms. The JDAPI utility (frmjdapi.jar) is included with the standard installation and is found in the /DEV_SUITE_HOME/forms/java directory.
There are commercial tools which can do so, one i personally know is FormsApiMaster.