You want to edit your card or you actually want to find a better fit to your trajectory?
If you just want to edit your card, Excel. If you want to better fit your card to your reality, Exbal has a function called "Trajectory Validation" wherein you tell it how far you were off and it tells you what muzzle velocity value would give you closer to what you're actually seeing in the field.
Occasionally the observed trajectory profile shown on the main form is consistently high or low at various distances. The can be caused by several things, for example: 1) muzzle velocity is higher or lower than specified on the main form; 2) the scope elevation click values are higher or lower than specified by the manufacturer, etc. Often the muzzle velocity value can be “tweaked” so that the resulting trajectory curve closely matches the observed trajectory path. To utilize the screen below, a series of shots from a bench rest after dialing in the best estimate of elevation adjustment for the target distance. Using two different target distances increases the robustness of the mathematical procedure used by Exbal to calculate a “tweaked” velocity value. In the example below a group of three shots were fired at both 500 and 600 yards. The come-up values were recorded and the error in elevation (should be zero when sight adjustments are used) was measured. When the Calculate button is clicked Exbal will attempt to calculate a best fit value for velocity. If one can’t be found an error message is popped up.