I had Botox between eyebrows injected yesterday. How long before I see the horizontal lines disappear?

botox effects take 3-5 days to take however... horizontal lines are treated by injecting the forehead above the eyebrows, not between the eyebrows.  That treatment take away the vertical lines

Because Botox (like Dysport and Xeomin) relaxes hyperactive muscles of expression that cause wrinkles, it is important to understand what to expect. The vertical lines between the eyebrows will be improved by injecting the corrugator muscle there, but will not have much effect on horizontal lines in the forehead. Horizontal lines require injection higher up, but this needs to be done expertly because they are often caused by the muscle that elevates the brows trying to overcome sagging brows. In that case, relaxing the muscle will make the lines go away but the brow can drop. Each area has its balance.

The horizontal lines along the upper nose are caused by a different muscles than the bulging muscles between the brows.  To control wrinkles, the "commas" and the horizontal "bunny" lines both areas require Botox injections.  Optimal results are obtained when the forehead, crows feet areas between the brows and top of the nose are injected with Botox.  Imagine a tug of war amongst the forehead muscles with one group pulling harder than the other.  By balancing these muscles the forehead look relaxed, without being frozen.