I have a function that creates a Pivot Table, but I am getting an error when I try to set a range that will be merged and have a title added to it.

In the below code, pivot_title_range is a 'String' variable, and is optional when calling the funtion. title_range is a 'Range' variable. Both lines that set the range (whether or not the users declares pivot_title_range) cause the same error.

If pivot_title_range = "" Then
    title_range = ActiveSheet.Range("B3:E4")
Else
    title_range = ActiveSheet.Range(pivot_title_range)
End If

Here is the error that I am getting -

Run-time error '91':
Object variable or With block variable not set

If required, here is a Pastebin of the full function - http://pastebin.com/L711jayc. The offending code starts on line 160.

Is anybody able to tell me what I am doing wrong? Thanks.