You want to show the current month, but when you select an other month you want to show an other month? Am I right?
If so, make a selectionbox for month, select one month and go to the properties of that selection box and check "Always One Selected Value" (optional)
Then go to Settings >> Document propeties >> tab: Triggers
Add an Action OnOpen
Add >> Selection in Field
Field : YourMonthField
Search String : =Month(Today())
This way when you open your document the current month get selected.
Is that what you are looking for?
(You can also add this trigger on Reload if you wish)