A calculation can take a date and return a date from the previous month. Data formatting on this calculation field can then show just the month name and year without the day.
Let ( D = DateField ; D - day ( D ) )
will return the last day of the previous month. Since you want to hide the day, this will be sufficient. If you use Get ( CurrentDate ) instead of DateField, be sure to make your calculation an unstored calculation or it will not correctly update with each new day's date.
Good suggestions, PhilModJunk. I found a suggestion in the help files, too, and this calculation works, too: Date(Month(Date Current) -1;Day(Date Current);Year(Date Current)), where Date Current is its own field. I tried using CurrentDate but could not get it to work right, but that would be better to just have one less field to have to deal with. Thanks for the help.
CurrentDate isn't a field, it's a parameter you pass to the get function that tells FilMaker to pull the current date from your computer's system clock. You can use get ( CurrentDate) in a field's calculation like this, but it won't update automatically when the date changes unless you also specify in storage options that the field be "unstored".
Got it! Your help was invaluable. This is the field calculation that does what I need: Date(Month(Get(CurrentDate)) -1;Day(Get(CurrentDate));Year(Get(CurrentDate))). Thanks for all the help.