Instead of doin the If Then Else functions just use Unit - Increase level of <ability> for (Researching unit). And you have to make an upgrade in the object editor, but make it do nothing. Just change the icon and description to whatever you want. Also the gold cost is there. Initial gold cost is how much the first level will cost and gold cost increment is how much more gold it will be for the next level. Example: initial cost is 50 and increment is 20: 1st level costs 50, 2nd costs 70, 3rd costs 90, 4th costs 110.
EDIT:
I just looked in object editor under upgrades and there is an effect called "Ability level bonus". So you can just use that for the upgrade and then you wont even have to trigger anything. Im not sure what you have to put for the base and increment values, im guessing just put 1 for both of them. But im not sure if this will effect every unit with that ability, aka you might only have to rersearch it one time and then all units will have the aura upgraded. Not sure if thats what ur trying to accomplish.