# Testing the Homogeneity of Slopes in Repeated measures ANOVA SPSS

I conducted a repeated measures ANOVA in SPSS, using the command Generalised Linear Model > Repeated Measures. I have a within subject factor with two levels (A), a measure (B) and a covariate (C). The within subject variables based on the factor are AB_1, AB_2.

According to the literature, ANCOVA has an additional assumption, the one of homogeneity of slopes. I have been trying to conduct the test in SPSS using the syntax commands I found here : https://www.ibm.com/support/pages/testing-homogeneity-slopes-hos-assumption-factorial-ancova-spss, which however refers to factorial ANCOVA. Specifically, I wrote:

DATASET ACTIVATE DataSet2.
GLM AB_1 AB_2 WITH C
/WSFACTOR=A 2 Simple(1)
/MEASURE=B
/METHOD=SSTYPE(3)
/PLOT=PROFILE(B)
/PRINT=DESCRIPTIVE HOMOGENEITY
/CRITERIA=ALPHA(.05)
/WSDESIGN=B
/DESIGN=C*A


I keep getting the following error:

A syntax error was detected in the effect specification where the symbol dur was encountered. Effect specification should have the following structure effect = BY-expression [WITHIN BY-expression [...]] BY-expression = variable [BY variable [...]] where variable is a factor or a covariate.

My question is if there's any was to test this assumption for repeated measures designs?