Getting maximum of raster in QGIS and use it in another algorithm

Question

I am developing a QGIS model in which I need to get the maximum of a raster. The Zonal Statistics makes a new layer, which I don't need. The html with stats is also not useful. I just need a numeric value can be use for another algorithm. Is it possible in QGIS model builder? (for more clarity: I get the maximum, then use it on another raster to take out 1m above and 1m below that maximum) Linked with above: How to treat inputs as variables, rather than the easier way of pulldown selections available in the graphical modeller So how do I tell he raster calculator in graphical modeller to do something like (dtm > min AND dtm < max) * dtm and while doing this to read the Input values float numbers?