What is findlastrow meant to be? Is it a variable of Range type? If so, you don't use an assignment statement, you use a set statement:
set object = otherobject
targetrange I'm guessing is meant to be a string. You're passing a range object to the format function (which takes two arguments, firstly a string, or something that can be converted to a string, secondly, a specific format).
If you actually got a valid range address into targetrange then teh third line would work. It's in the two previous lines it's not working. What are those two lines actually meant to od?