Linetype SHX files

Hello,

I have a linetype SHX file and a linetype LIN file - that's it.  I do not have the source SHP files for the SHX.

I want to add additional custom linetypes to the LIN file and have them referenced from the same SHX file.

I've attached the 2 files.

We are working in 2011.

Is this possible?

Thanks!

Andrew