CG - Using Matrix as texcoord

I'm trying to use a float3x3 matrix as a texcoord inside the vertexOut struct, defining it as:

float3x3 local2WorldTranspose : TEXCOORD5;

Returning that from vertex function.

o.local2WorldTranspose = float3x3(tangentWorld, binormalWorld, normalWorld);

To use that in the fragment function to avoid defining it there uselessly (and taking up some pixel power)

In the fragment I use it like this:

float3 normalDirection = normalize(mul(localCoords, o.local2WorldTranspose));

It should take 3 texcoords so TEXCOORD5 should be fine.

But it gives me error:

GLSL translate vertex: Unsupported element type in struct for shader return value (mat3) at line 15

This only happen with GLES complilation, is it possible to use that instead of passing single texcoords and then define a matrix in the fragment ?