Seems like you have the basic idea down. Have you looked at anything else that gives blindsense? Blindsense is a Racial Special so you will need to bootstrap it onto the template. This way when you apply the template the Blindsense Racial Special comes along.
Then the script would look like the following and as your going after Hit Dice you have to be At least "Post-Levels/100". So I would go
Post-Levels/10000
Code:
~ Set the total blindsense range of 5 times the hit dice
~ into a local variable.
field[abValue].value += herofield[tHitDice].value * 5
~ Add our local variable total into the Blindsense ability.
#value[rBlindsen] += field[abValue].value