How can I use function from Regression model for new predictions . ?

I have used n X 4 matrix in Regression App. First three columns are independant variables and 4th column is response variable. I created one tree model in app and imported the same in matlab in the format of function. The function looks like this : function [trainedModel, validationRMSE] = Model_Fine_tree_wo_stand(trainingData).....

Now I want to use new data to predcit new values. How can I do that ? My input data wll be n x 3..

(I dont want to use struct model to predict the values, I want model in function / script format)

Thanks in advance