Use Variable For AutoFill Range

I am creating a loop that will autofill 16 cells down. It copies the formula from one cell (Z230), pastes that 16 cells down (cell Z246), then changes the lock properties of the cell (Z246) before autofilling down 16 (to cell Z261). At which point the loop starts over again. (copies cell Z246,pastes it to Z262, fills down 16 , etc)

Because the cell I am copying from changes in each loop, I set a variable to grab the address of the starting cell and last cell of the copy.

I then put this into a String so it would return something like this

Range("Z245:Z259")

Problem is I get extra quotes around Range("Z245:Z259") - it comes out as string "Range("Z245:Z259")"
This gives me a problem when I try to replace

Selection.AutoFill Destination:=Range("Z245:Z246"), Type:=xlFillDefault

with


Selection.AutoFill Destination:=rangevariable, Type:=xlFillDefault

Below is my total code, but I get stuck on the selection line. I have to do this 300 times so I would prefer not to do it manually!