got a #value error-You're having problems because those date/times aren't in a format that Excel recognizes as such.
Does this work for you?
=SUBSTITUTE(REPLACE(B2,LEN(B2)-1,0," ")," ",", ",2)-SUBSTITUTE(REPLACE(A2,LEN(A2)-1,0," ")," ",", ",2)
company policy wont allow me it blocked me when i tried.Perhaps if you could download the xl2bb plugin and post an actual sample of your sheet, rather than an image, because my sample looks the same as your text and it works for me.
XL2BB - Excel Range to BBCode