iPod touch Upgrading from iOS 4.1 to 5.1 without jailbreaking

[chiastic.slide]

Hi,
I found a forgotten iPod Touch 4th Generation in the house that has 4.1 iOS installed. I want to know if there is a way to upgrade it to 5.1 without jail breaking. I know I can upgrade it to iOS 6 but I'd rather have 5.1.

Any help would be really appreciated.
Thanks

 

[Intell]

Yes, but only if you have your SHSH blobs for iOS 5.1.X.

 

[chiastic.slide]

Thanks for the quick reply.
Unfortunately I haven't done that