Have you looked into the Automatic Load Combination generation feature of the GUI? It comes built-in with rules for a few standard codes used in US, Britain, etc. The attached document describes the procedure for using it.
If you are looking to create your own set of rules, here are the steps. Let say that we want to create one called "Norwegian".
1) Go to Commands | Loading | Edit Auto Load Rules. The ‘Edit Loading Rules for Auto Load Combination Generation’ window appears.
2) Click on ‘New Code’ and in the ‘Code Name’ specify the name of the Norwegian design code and click on ‘OK’.
3) Then, click on ‘New Category’ and specify any ‘Category Name’. Also, specify the ‘Number of Rules’ which refer to the number of possible load combinations. Click on ‘OK’.
4) In the table that appears (where number of rows is equal to the number of rules specified and number of columns is equal to the number of possible load cases: coloured yellow), provide the load factors for the particular load cases for consideration in the load combinations. You can also add additional load combination factors by clicking on ‘Add Row’.
5) Click on ‘Update Table’ after you have finished and then click on ‘Close’.
After that, if you go to Commands | Loading | Automatic Load Combination, you can select the Norwegian code under the drop-down list of ‘Select Load Combination Code’ and also select the category name under the ‘Select Load Combination Category’ drop-down list. Click on ‘Generate Loads’ after making the selections.