Hi
First you find the fmx name of the form for which you want to get the FMB by nagivagint to the form and then help
then you will get the location as
../.../INV/11.5.0/forms/US/INVMST.fmx
then you navigate to $AU_TOP/11.5.0/forms/US
here you will find the same form name with INVMST.fmb
bye
Raghuram