New to the forums and was hoping for some help with writing out part of a non-linear regression model from somebody brighter than me.

So one part of the model contains a Boolean expression and goes something like this

X=TL if T>TM or X=TU if T>TM

So for each iteration, T is supposed to be compared with the estimated TM so that if T<TM is true and T>TM is false then X=TL and vice versa.

Fairly new to SPSS and this might be really simple, but I just don't know how to syntax this into the model, I simply can't write it out correctly, which is very frustrating . I have PASW 18. If any of you could help me it would be most appreciated

Thanks so much for your help