Simple effects estimate statement

I am confused how to do this (generate the simple effect hours at a specific level of categorical variable prog). Note this is the same estimate statement substantively used by proc glm.

proc plm restore = catcont;

estimate 'hours slope, prog=1 jogging' hours 1 hours*prog 1 0 0,

'hours slope, prog=2 swimming' hours 1 hours*prog 0 1 0,

'hours slope, prog=3 reading' hours 1 hours*prog 0 0 1 / e;

My problem is this example uses a variable that has 3 levels, two dummies are then created (reading is the reference level). My data already has the dummy variables split out (using this example I would already have a dummies for jogging and for swimming coded one/zero). If I want to know the simple effect of hours at the level jogging, how do I code this?.