Hi Blair,
There's a very simple option for this - without any GUI programming on your side. The IFM function IfmEditProperties (available since FEFLOW 6.2) provides the functionality to bring up a Qt dialog for IFM data input from within FEFLOW. The dialog is customizable, and it supports lots of data types (integers, doubles, enumerations, strings, pathes, time, selection from a list of all time series in FEFLOW, selection from all nodal or elemental user distributions). Please have a look at the description in the FEFLOW help system.
There is also a (very simple) test example in the FEFLOW SDK data (C:\Users\Public\Documents\WASY FEFLOW 6.2\sdk\ifm\samples\simul\ifm_prop).
Good luck - and don't hesitate to ask if you struggle with the functionality!
Peter