Unable to set Source Current for SMU (Four Point Probe Experiment)

Hi, I am currently working on a project that requires the usage of four point probe and a 2450 SourceMeter. Currently, my four point probes' cables are connected to the rear end of the SourceMeter. During my experiment, the current source changes from time to time, leading to inaccurate resistance measurements. When I tried to change the source back to what I wanted, a message pop up showing "This setting cannot be changed when measure function is resistance. Would you like to switch to SIMV(Ω)". Pressing the button (Yes) took me out of the Ohmeter mode to two wire sense Voltmeter. Somehow I can't figure out a way to change my source current. Would love to have some help.