You could do this if you control all the data entry through Forms. Assuming the field is of numeric datatype, you could use the "AfterUpdate" event on that field to add 10000 to that field upon entry.
So if the field was named something like "MyValueField", that VBA code would look something like:
Code:
Private Sub MyValueField_AfterUpdate()
If Me.MyValueField < 10000 Then Me.MyValueField = Me.MyValueField + 10000
End Sub
To see where to put this VBA code, if you open your Form in Design View, right click on the field and select "Proprties", go to the Event tab and on the "After Update" line, select the "Code Builder" option and enter your code there.