Changing Materials

[gattispilot]

I have a mesh that I want to change the material setting on it with the press on a key.

I have this: where a key is pressed and it goes to the revertlaser

MESHHANDLE tank = oapiLoadMeshGlobal ("LASER2");

    case OAPI_KEY_W: // fire
 {
            Revertlaser();
            return 1;
        }



void LASER2::Revertlaser (void)
{
PlayVesselWave3(JohnSoundID,CANNON,NOLOOP,255);     
MATERIAL *mat = oapiMeshMaterial (tank, 1); // first you point to the material.
            mat->diffuse.a  = 1;          // then you change the alpha value to 0.025 on the diffuse line
            mat->diffuse.g  = 0.015686;
            mat->diffuse.b  = 0.694118;
            mat->diffuse.r  = 0.694118;
              
            mat->ambient.a  = 1;          // then you change the alpha value to 0.025 on the diffuse line
            mat->ambient.g  = 0.015686;
            mat->ambient.b  = 0.694118;
            mat->ambient.r  = 0.694118;       // 0.1 on ambient alpha
             
            mat->specular.a  = 1;          // then you change the alpha value to 0.025 on the diffuse line
            mat->specular.g  = 1;
            mat->specular.b  = 1;
            mat->specular.r  = 1;       // 0.1 on ambient alpha       //etc..
            mat->emissive.a = 1;
            mat->emissive.g  = 0.015686;
            mat->emissive.b  = 0.694118;
            mat->emissive.r  = 0.698039;
    
          
            
            

}

Here is from the mesh:
MATERIALS 17
material01
tread
material04
black
light
orange
grate
wheeld
red
dkgrey
panel
logo
logo1
wheele
wheelgrey
material02
laserbeam
MATERIAL material01
.909804 .909804 .909804 1
.909804 .909804 .909804 1
1 1 1 1 20
0 0 0 1

But I can not see the material change take effect