Is there any way to install themes, software etc. on my BB without
the data cable? I'm on a business trip and don't have my cable or
my desktop software.

Wondering if theres a way to install once I email the software to my
BB.

No, but depending on what application it is you might get an OTA version.

One of the expense report programs. Like

Expense manager + or
PAI Expense

OTA version????