We claim the ornamental design for a display panel of a programmed computer system with a graphical user interface, as shown and described.
FIG. 1 is a first image of a front view of a display panel of a programmed computer system with a graphical user interface; and,
FIG. 2 is a second image thereof.
The broken line showing of a portion of a display panel is for the purpose of illustrating environmental structure and forms no part of the claimed design. The broken lines showing of portions of the graphical user interface within the display panel form no part of the claimed design.
The subject matter shown in FIGS. 1-2 includes a process or period in which one image transitions to another image. This process or period forms no part of the claimed design.