Report Expression Help

I have 2 cognos report expressions i need them to be converted into an SSRS exppression... Has someone done it ..?

first -of-month (datetime-to-date(make-datetime(?Year?,?BePeriod?,1)))....

last-of-month (datetime-to-date(make-datetime(?year?,?EndPeriod?,1)))...



 "Activity from: January 1, 2011 thru Period Ending January 31, 2011 " This is the Intended output i am trying to get into my SSRS report header

I have 3 report parameters

Year
BegPeriod
EndPeriod

FM