You don't need it. The extruder steps are saved to the EEPROM configuration from within Repetier. Do your calibration, then once you figure out what your stepper value should be you can save it to the EEPROM.
What I do is mark the filament with a marker every 10mm (about 6-7 marks), then I extrude 10mm. If it extrudes more (past the next marker), I use the retract command set at 1mm, and back up the filament until I see the marker it overshot, while counting how many times I clicked the retract button. Lets say you over extruded 3mm. From the original E Steps setting (eg. E138), substract about 10 for every mm that you went over. So in the example above, you would have 138- (10 x 3mm) = 108.
On the Command Line, type M92 E108, hit ENTER, then extract 10mm again. Is it close? Work with this back and forth until you find the exact value for your machine. Once you're happy with it, you can save the value to your EEPROM like it was mentioned beore, or you can enter the value as part of your start GCODE in the slicer settings.
To print or, 3D print, that is the question...
SD3 printer w/too many mods, Printrbot Simple Maker Ed., FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.