Obtaining covariance terms involving the intercept term in a linear regression using SPSS

The covariance terms associated with the intercept (or constant) in SPSS obtained by firstly computing a column where every element equals 1.

COMPUTE CONST=1.
EXE.

The above created constant term may then be added as a predictor in, for example, a moderation analysis, after removing the default option to include the intercept (constant) in the analysis (using the /ORIGIN subcommand) and requesting the covariance matrix of the regression coefficients (using the /BCOV subcommand).

REGRESSION
  /MISSING LISTWISE
  /STATISTICS COEFF OUTS BCOV R ANOVA
  /CRITERIA=PIN(.05) POUT(.10)
  /ORIGIN
  /DEPENDENT Y
  /METHOD=ENTER CONST ZX ZM ZXM.