If I understand your question, I think easiest would be...from the main menu script the button to open a new window. You can select the size and location of the window. Select the Modal style of window, so the user has to type in this window and dismiss the window (user can't leave window until they dismiss it).
On the main screen, put the button in the tab order, attach the OnObjectEnter trigger to further automate the process. The first line of the script can be a Show Custom Dialog script step giving user a choice to enter patient details. Then open new modal window, etc.
You might also want to use a portal in it's own panel in a tab control to record this info. The result is somewhat similar and does not require any scripting.
Thanks guys, I'll have to become more familliar with portals and modal windows. I'm on the trail, thanks for the start you guys!!