[TYPO3-english] Including typoscript templates through setup field?`

[Stig Nørgaard Færch]

I know it's possible to include typoscript from typoscript setup through 
<INCLUDE_TYPOSCRIPT:somefile>.

What I'm looking for is the possibility to include typoscript templates 
(sys_template) conditionally.

Let's say that some constant is set to 1, then I want template A to be 
included.
If the constant is set to 2, then I want tempalte B to be included.

Is this somehow possible?

/Stig