Several options exist to create a GUI front end for your Fortran application. I currently use Winteracter (14.0 as of this writing). However, another cross-platform option exists with DISLIN.
To get a flavour for what can be done with DISLIN, visit "Using DISLIN to make a GUI for a Fortran Program." Note that DISLIN is free for non-commercial use. Licenses for commercial use or for just supporting DISLIN are available from this site.
DISLIN supported operating systems include UNIX, Linux, FreeBSD, OpenVMS, Windows, Mac OSx, and MS-DOS. DISLIN distributions are available for a number of languages under Windows 64-bit including Absoft Pro Fortran, FreeBASIC, gcc, g++, gfortran (Cygwin and Mingw64), Intel icl and ifort, Julia, Java, NAG Fortran, Portland Visual Fortran, Perl, Python, R, Silverfrost Fortran (FTN95), MS Visual C++. DISLIN .NET 64-bit distribution includes language (compiler) support for C#, Visual C++ .Net, Visual Basic .NET 64-bit.
Right click on the applicable .zip file for your compiler and save a copy of the file to your computer.