Raster Interaction with Model Builder - Allowing a user to select the user inputs

[JustinGleeson]

I have a basic model that uses Raster Iteration to process all of the rasters in a .gdb. The model allows the user to define a weighting in the GUI and then the model runs a raster calculation on each iteration, stores the results in Collect Values and finally does a Cell Statistics calculation ton create the final output. 

As of now the Raster Iteration runs through all rasters in the .gdb. Is there a way of providing the user with a checkbox/radio button in the GUI to just choose a selection of the rasters in the .gdb?

The image below shows the model and the GUI. Ideally I'd like to be able to select the required rasters in the GUI before assigning the weightings.

Any advice or links on this would be great.

Many Thanks Justin

[ShitijMehta]

sorry was on leave.

Yes pls modify the validation code

[JustinGleeson]

OK, thanks.

I'll give it a go then and see what happens.

Thanks

Justin