Custom Error use in Roofit for binned fitting

I have been facing a problem regarding the use of custom errors in roofit (root version 5.32.04) for RooDataHist. By changing scale factor to any other value for the bin error it shows the proper errors in plot, but the final fitting results remain unaltered even by using RooChi2Var.

Can anybody suggest me how to use custom errors in final roofit fitting ?

I have attached my code below.

Thanks in advance
custom_error.tar.gz (3.21 KB)