What is the formula to bring the current last date from period hierarchy

Iam working on Hyperion financial Reporting.i have created a grid with 2 dimensions(entity and period).My requirement is that the current last date of the period hierarchy should be displayed automatically in the header when the report is run.what formula should i write in the textbox to bring the current last date.Moreover i dont want to create a prompt for the period dimension.
Kindly help me on this.
thanks in advance.


Thanks for all your replies..
My actual requirement is that I have a period dimension with year,month and week as members.I dont want to set period as a UserPOV or a prompt.but i want the last date of current week of the period diemnsion to get automatically displayed in the text box which is placed on the header when the report is run.Period dimension is not used anywhere else in the report.I've tried using another grid for the period and i've hidden it.but what formula should I use to to display the last date of the week on the header.I tried using the function Bottomofhierarchy but it wasn't helpful..
Please help me on this.