non estimated interaction between continuous and categorical variables in mixed model

[FI]

Hi,

I am trying to run an ANCOVA test. here I have one continuous variable (PreN). But SAS cannot estimate this effect on ANOVA table. It gives me 0 DF and non-estimated F and P values.

I used this model.

proc mixed data=mBiomMMMm plots=residualpanel;
class Year Trt Block Plot;
model BiomN = Trt Year Year*Trt PreN*Trt Block/ solution;
repeated Year / type = ar(1) subject = Plot(Trt);

lsmeans Trt / cl;

run;

 The continuous variable is in the interaction with a categorical variable (Trt).

What can do to fix this problem and get the estimated value of precipitation?

Please let me know if you know how I can fix this. I need the answer very soon.