Hi Dee, I'd be wary of using a butter substitute. The reason is that it's likely to be processed, and cooked at extremely high temperatures, which destroys the nutrients and causes it to resemble plastic more than food!
I can't remember if I wrote this anywhere here but they have to dye margerine yellow because it's black after the processing. Just the word 'substitute' concerns me, because it probably means it's man made and processed. I hope this helps.