Attaching document means they are using hyperlink action of tally. Yo can get a number of example from this forum. One advantage of that TDL is browse option . That is done with DLL . We can connect and use number of DLL/ com files for this purpose. I think The DLL file they have used is their own DLL file. That DLL/Com file return as string value full path of a file which is selected. for develop a dll file one must know at least VB Example of connecting to DLL file is there in sample tdls of Tally given along with developer. Main challenge is either you must have a dll with licence to use or you have to develop own DLL
@Sanskruti, I am completely agree with Mr. Jobimon. But lets have a look in detail about the task. There are two stages to complete this task. 1) Browse File 2) Show File For step 1 you must use .dll file either you should purchase any one or develop it by yourself. It is better to develop C++ COM Library so that it can be easily called by $$CallDLL function from tally. You have to register that assembly with operating system on which you are installing your customization. If you are developing your dll in .Net then you must register your dll with regasm.exe which is in framework folder of microsoft in Windows system folder. You can register your .net Dll with regasm.exe with the help of command prompt. For step 2 you can use Browse URL action to open or show specified file.
You may use a C#.net version of file browser as below: https://www.codeproject.com/Articles/15059/C-File-Browser
Or you may also use comdlg32.dll (windows inbuilt program) to suit your needs... PS you will have to call GetSaveFileNameA from DLL...