Shortcut for changing (not all) but selected text in layer to specific font family

This is a demo that splits your text layer at the return character and formats just one piece. I use this basic process in numerous text processing scripts. Sorry for the lack of comments, again this is just a framework.

#target photoshop

layerUpdate();

function setFormatting(start, end, fontName, fontStyle, fontSize){
    var idsetd = app.charIDToTypeID('setd');
    var action = new ActionDescriptor();
    var idnull = app.charIDToTypeID('null');
    var reference = new ActionReference();
    var idTxLr = app.charIDToTypeID('TxLr');
    var idOrdn = app.charIDToTypeID('Ordn');
    var idTrgt = app.charIDToTypeID('Trgt');
    reference.putEnumerated(idTxLr, idOrdn, idTrgt);
    action.putReference(idnull, reference);
    var idT = app.charIDToTypeID('T   ');
    var textAction = new ActionDescriptor();
    var idTxtt = app.charIDToTypeID('Txtt');
    var actionList = new ActionList();
    var textRange = new ActionDescriptor();
    var idFrom = app.charIDToTypeID('From');
    textRange.putInteger(idFrom, start);
    textRange.putInteger(idT, end);
    var idTxtS = app.charIDToTypeID('TxtS');
    var formatting = new ActionDescriptor();
    var idFntN = app.charIDToTypeID('FntN');
    formatting.putString(idFntN, fontName);
    var idFntS = app.charIDToTypeID('FntS');
    formatting.putString(idFntS, fontStyle);
    var idSz = app.charIDToTypeID('Sz  ');
    var idPnt = app.charIDToTypeID('#Pnt');
    formatting.putUnitDouble(idSz, idPnt, fontSize);
    textRange.putObject(idTxtS, idTxtS, formatting);
    actionList.putObject(idTxtt, textRange);
    textAction.putList(idTxtt, actionList);
    action.putObject(idT, idTxLr, textAction);
    app.executeAction(idsetd, action, DialogModes.NO);
	}

function layerUpdate(){
    if(documents.length > 0){
        //declare demo variables
        var text1 = "test";
        var text2 = "test replacement";
        var oldtSize = 48;
        var tSize = 24;
        var tFont = "Calibri";
        var tStyle = "bold";
        var tLead = 24;
        var boxH = 200;
        var boxW = 400;
        var tColor = new SolidColor;
        tColor.rgb.hexValue = "FF0000";
        //end demo variables
        var originalDialogMode = app.displayDialogs;
        app.displayDialogs = DialogModes.ERROR;
        var originalRulerUnits = preferences.rulerUnits;
        var j = 0;
        try{
            var docRef = activeDocument;
            preferences.rulerUnits = Units.POINTS;
            var m = 0;
            for(var i = 0; i < docRef.artLayers.length; i++){
                var LayerRef = docRef.artLayers[i];
                if(LayerRef.kind == LayerKind.TEXT){
                    var TextRef = LayerRef.textItem;
                    TextRef.textComposer = TextComposer.ADOBESINGLELINE;
                    var layerText = TextRef.contents;
                    var newText = layerText.replace(text1, text2);
                    if(newText != layerText){
                        j = i;
                        TextRef.contents = newText;
                        if(TextRef.size == oldtSize){
                            TextRef.size = tSize;
                            TextRef.font = tFont;
                            TextRef.useAutoLeading = false;
                            TextRef.leading = tLead;
                            TextRef.color = tColor;
                            var l = TextRef.contents.split(/\r/);
                            docRef.activeLayer = LayerRef;
                            setFormatting(0, l[0].length, tFont, tStyle, oldtSize);
                            preferences.rulerUnits = Units.PIXELS;
                            if(TextRef.kind == TextType.PARAGRAPHTEXT){
                                TextRef.height = boxH;
                                TextRef.width = boxW;
                                }
                            preferences.rulerUnits = Units.POINTS;
                            break;
                            }
                        }
                    }
                }
            }
        catch(e){
            alert(e + '  ' + e.line);
            preferences.rulerUnits = originalRulerUnits;
            app.displayDialogs = originalDialogMode;
            return;
            }
        preferences.rulerUnits = originalRulerUnits;
        app.displayDialogs = originalDialogMode;
        }
    else{
        alert('You must have a document open to run this script.');
        return;
        }
    }

To be blunt: 

While this may be possible via Scripting (with some workaround to determine the selected range) I would recommend doing type-heavy work in more appropriate software (Indesign, Illustrator, … for example).