[Glad you worked it out but I'll leave this posted anyway.]
The EQU instruction looks at two numbers, either constants or memory locations, and gives a TRUE if they are equal.
'Source A' and 'Source B' are just the names of the two values you give to the EQU instruction. Other than both items being used by the instruction they have not other relationship to each other.
In two of your instructions the 'Source A' value was set as S:40. The 'Source B' value is given as a constant number. The 'Source B' value could just as easily have been a VARIABLE value, for example N7:0 as KidBlue suggested.
Try changing 'Source B' in one of the instructions To an unused 'N' address. (N7:0 is just an example) Then download the changed program (if you weren't changing it online. Then, using RSLogix 500 change the value in the N data table. You will see the value also change in the instruction. Verify that the effect is what you want. When satisfied set up the Panelview program to change the selected N address just as you did from RSLogix.