There was a question asked on the forum on how to hid a subpage. There is no Peoplecode function to hide a subpage directly, BUT one way around that is putting the subpage in a group box and hid the group box instead. Hiding the group box will end up hiding your sub page
Make sure to follow the following post, it will walk you through how to hide a group box on a page.
To hide a group box and all the fields placed in it on a PeopleSoft page use the code below in a page “Activate” event.
HR_LBL_WRK.STATUS_LBL.Visible = False;
Where HR_LBL_WRK is the record name, and STATUS_LBL is the field record. Double click on the Group Box to see its record properties (1st tab).
For the Group box and all the fields in it to be completely hidden, make sure the “Hide Border” and “Adjust Layout for Hidden Fields” on the Label tab are checked and the “Hide all Fields when Group Box Hidden” on the Use tab is also checked.