A simple (I think) Model Builder question. I have 25 field sites, for each of which I have mapped land use as separate layers for different years. In one folder I have veg layers for 1994, named tara{site number}veg94 (eg., tara01veg94.shp, tara02veg94.shp, through to tara25veg94.shp). In the other folder I have the same for 2007, similarly named by site number (tara01veg07.shp, tara02veg07.shp ... tara25veg07.shp).

I am wanting to union the layers for each site for successive years together using a model, for example tara01veg94.shp unioned with tara01veg07.shp to create tara01veg9407 and so on. I presume that I need to use an iterator to specify the site number for each run of the union function and then insert the %value% created by the iterator into the input and output file names. The problem I'm having is that I need to iterate the same site number for two input files simultaneously, so I figured the "for" iterator was the one to use, but the union function doesn't let me put %Value% into the input fields (though it accepts it in the output field ok). Any help would be greatly appreciated... thanks.