Here's how I'd try to do it, assuming (a) +15V and -15V fixed supplies are available, (b) the digital pots have a maximum resistance of 100k each, and (c) independent control of the + and - adjustable supplies is required.
R1 and R4 are selected to prevent the digital pot voltage rising above ~ 3V, for compatibility with the micro controller .
U1 and U3 are unity-gain buffers. One can be omitted if a single pot is required to control both variable supplies so that they track each other.
U2 and U4 are respectively non-inverting and inverting amplifiers, each with a gain of ~ 4. The opamps need to be rail-to-rail I/O types if a wide control range is required.
M1 and M2 provide power gain. Feedback is taken from across the loads to stabilise the output voltages.