A goal becomes easier to track when you can say what it is for, how much it costs and when you would like to reach it.
Write down the estimated cost, what you have already set aside and how much time remains. Divide the difference by the number of remaining contribution periods. If the result does not fit your current spending plan, try a later date, smaller goal or different contribution schedule.
Keep a simple record of contributions and review it when expenses or income change. Update the amount if the price changes. A goal worksheet is useful for seeing which part of the plan moved.
Further reading: CFPB Your Money, Your Goals worksheets.