Analyzing bovine mastitis with mixed model in SPSS

#1
Hi.
I´m a PhD student working in bovine mastitis.
I’m trying to analyze a longitudinal study using SPSS version 15.
The study consists of 100 cows sampled once a week during 9 months. Each cow has 4 glands (identified with numbers 1, 2, 3 and 4) and I have sampled each gland at each time point.
At each time point, a gland can be either healthy or infected; hence a given caw can have 0, 1, 2, 3 or 4 infected glands. Infections are quite stochastic and an infected gland can be non infected in the next sample point and again infected in the following sample point or vice versa.
I am interested in the effect of the udder infection and the sample time in the concentration of a milk protein named lactoferrin. I have determined the concentration of this protein in each sample and now I am trying to model the lactoferrin concentration using sampling time (1 to 9) and infectious status as explicative factors. I want to include caw as a random factor and mammary ID as a subject nested within caw. However I’m not sure if this is the right option and, in case it is, I am having problems to set the model using the dialog box Mixed models of SPSS version 15.
Can anybody give me a piece of advice in this matter? I would really appreciate your help
Thank you very much
Luciano