Yes it is possible. There are a few threads in other RC forums describing how.

You might want to first read about the basics of Pronto Hex at
[Link: remotecentral.com]

The threads on merging Pronto Hex cover the aspects of Pronto Hex you need, but reading the above document may be more understandable. Either way you need to understand splitting a signal into header, one-time portion, and repeat portion. Then put those three parts of the merged signal together.

You may also want to experiment with removing the repeat portion from one (or both) of the signals. A Toshiba TV probably doesn't need the repeat portion of the NEC1 signal, but I'm not certain of that.

A merged signal must have:
A) the One-time portion of the first command.
B) zero or more copies of the repeat portion of the first.
C) the One-time portion of the second.
D) zero or more copies of the repeat portion of the second.

A, B and C must all be in the one-time portion of the merged signal. For use instead of a macro, D could also be in the one-time portion.