Help with extrusion animation

Hi am really new to blender and animation, have been teaching myself via online tutorials. Am wanting to create a simple animation where an object extrudes along a curve. have managed to add a circle as a bevel object along a curve which worked fine but am having trouble animating the movement. When I go to add keyframes the yellow keyframe line in my timeline does not go all the way to the top of the timeline, when I add new keyframes to show the circle’s extrusion along the line (by pressing i whilst hovering over the objects properties) and by changing the end value of the bevel factor I cant see any changes when I scrub through my timeline. Have been searching forums and tuts but cant find anything! Have been making sure I set start keyframes in the timeline, I feel like I’m missing something really obvious!! Haaaaalp

Well, i could not quite get what keyframes you add where and which place is this yellow keyframe line (could it be that myriad of automatically inserted keyframes trick you in thinking this is a line?) but hovering over the Bevel Factor Start and End input fields and hitting “i” is the same i would do. Difference likely is that i’d keyframe frame “1”, then move Timeline position to some frame in the middle of strip, move Start and End Bevel sliders and hover/hit “i” again. Repeat one or two more times - done.