Multivariate Linear Regression

I wonder if anyone can help me. I am trying to do a multivariate linear regression, I have 3 dependent variables with 2 separate time points for each, how do I condense this into three variables so that I can look at the time points together.
Hi dani.alle,

could you write more regarding your data and research question? So you consider three different outcome / dependent varibles, each has been measured at two different time points? Do you have any other predictors/independent variables? What is your research question?