This formula should work for you.
A B C
<TABLE style="WIDTH: 187pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=249><COLGROUP><COL style="WIDTH: 58pt; mso-width-source: userset; mso-width-alt: 2816" width=77><COL style="WIDTH: 65pt; mso-width-source: userset; mso-width-alt: 3181" width=87><COL style="WIDTH: 64pt; mso-width-source: userset; mso-width-alt: 3108" width=85><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 1pt solid; BACKGROUND-COLOR: #b8cce4; WIDTH: 58pt; HEIGHT: 15pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl64 height=20 width=77>
Sch. Time</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: #b8cce4; WIDTH: 65pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 0.5pt solid" class=xl65 width=87>
Dept. Time</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: #b8cce4; WIDTH: 64pt; BORDER-TOP: windowtext 1pt solid; BORDER-RIGHT: windowtext 1pt solid" class=xl66 width=85>
Delay</TD></TR><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext 1pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 15pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl67 height=20 align=right>
11:00 PM</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl63 align=right>
11:30 PM</TD><TD style="BORDER-BOTTOM: windowtext 0.5pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 1pt solid" class=xl68 align=right>
0:30</TD></TR><TR style="HEIGHT: 15.75pt" height=21><TD style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: windowtext 1pt solid; BACKGROUND-COLOR: transparent; HEIGHT: 15.75pt; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl69 height=21 align=right>
11:00 PM</TD><TD style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 0.5pt solid" class=xl70 align=right>
12:05 AM</TD><TD style="BORDER-BOTTOM: windowtext 1pt solid; BORDER-LEFT: windowtext; BACKGROUND-COLOR: transparent; BORDER-TOP: windowtext; BORDER-RIGHT: windowtext 1pt solid" class=xl71 align=right>
1:05</TD></TR></TBODY></TABLE>
<TABLE style="WIDTH: 100pt; BORDER-COLLAPSE: collapse" border=0 cellSpacing=0 cellPadding=0 width=133><COLGROUP><COL style="WIDTH: 100pt; mso-width-source: userset; mso-width-alt: 4864" width=133><TBODY><TR style="HEIGHT: 15pt" height=20><TD style="BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: transparent; WIDTH: 100pt; HEIGHT: 15pt; BORDER-TOP: #f0f0f0; BORDER-RIGHT: #f0f0f0" class=xl65 height=20 width=133>
=MOD(B2-A2,1)</TD></TR></TBODY></TABLE>
=MOD(Dept. Time - Sch. time,1)
This video will explain why this works.
http://www.youtube.com/user/excelisfun#p/search/0/btiuexHSvHY