I have my own schedule for a job but i need to show the differences between my schedule and another persons schedule (for the same job of course) on my own schedule.

which column should i use for entering his dates? it will not be one to one matched activities but i can still match many items or at least summary activities so that is no problem but i like to know which column should i use for entering and then for comparison too

for example to enter their start and finish dates should i use one of the start1,2,3,4.... and finish 1,2,3,4 columns?

and then how can i show the difference between my finish and start dates and his finish and start dates? i dont need to enter his links , just entering his dates are enough (i didn't see how i can enter his links anyway)

You can use any of the spare date fields you like - Start1 etc or Date1. To show the difference use a spare Duration (Duration1) column to calculate the difference between the two dates. DateDiff or ProjDateDiff functions should work.

It may not be what you are looking for, but if you have the same tasks (as in same name) I woul duse th ecompariosn feature (Under Project/ Compare Reports). This will give you all dates for both programmes, as well as a visual indicator of where the differences are. I have found this useful, especially for larger projects, where a visual can save an awful lot of time.

Quick note for clarification: the Compare Projects tool will only work on two copies of the same file. If the OP created a project and the other user created a separate project file, the Compare Projects tool won't work.

yes my project and his are totally different files with similar but different WBS. so i can use key and common activities from his schedule to compare my dates but not everything on our schedules is done the same way.

Then you cannot use the compare project utility. You'll need to manually enter his dates into spare fields and perform the calculations in a duration field.