Try a VLOOKUP:
Excel 2003<TABLE style="BORDER-RIGHT: #a6aab6 1px solid; BORDER-TOP: #a6aab6 1px solid; BORDER-LEFT: #a6aab6 1px solid; BORDER-BOTTOM: #a6aab6 1px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff" cellPadding=2 rules=all><COLGROUP><COL style="BACKGROUND-COLOR: #e0e0f0" width=25><COL></COLGROUP><THEAD><TR style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0; TEXT-ALIGN: center"><TH></TH><TH>A</TH></TR></THEAD><TBODY><TR><TD style="COLOR: #161120; TEXT-ALIGN: center">1</TD><TD style="TEXT-ALIGN: right">756</TD></TR><TR><TD style="COLOR: #161120; TEXT-ALIGN: center">2</TD><TD style="TEXT-ALIGN: right">30</TD></TR></TBODY></TABLE><TABLE style="BORDER-RIGHT: #a6aab6 1px solid; BORDER-TOP: #a6aab6 1px solid; BORDER-LEFT: #a6aab6 1px solid; BORDER-BOTTOM: #a6aab6 1px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff" cellPadding=2 rules=all><THEAD><TR style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0; TEXT-ALIGN: center"><TH>Sheet1</TH></TR></TD></THEAD><TBODY></TBODY></TABLE>
<TABLE style="BORDER-RIGHT: black 2px solid; PADDING-RIGHT: 0.4em; BORDER-TOP: black 2px solid; PADDING-LEFT: 0.4em; PADDING-BOTTOM: 0.4em; BORDER-LEFT: black 2px solid; PADDING-TOP: 0.4em; BORDER-BOTTOM: black 2px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff" cellPadding=2 rules=all width="85%"><TBODY><TR><TD style="PADDING-RIGHT: 6px; PADDING-LEFT: 6px; PADDING-BOTTOM: 6px; PADDING-TOP: 6px">Worksheet Formulas<TABLE style="BORDER-RIGHT: #a6aab6 1px solid; BORDER-TOP: #a6aab6 1px solid; BORDER-LEFT: #a6aab6 1px solid; BORDER-BOTTOM: #a6aab6 1px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff; TEXT-ALIGN: center" cellPadding=2 rules=all width="100%"><THEAD><TR style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0"><TH width=10>Cell</TH><TH style="PADDING-LEFT: 5px; TEXT-ALIGN: left">Formula</TH></TR></THEAD><TBODY><TR><TH style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0" width=10>A2</TH><TD style="TEXT-ALIGN: left">=VLOOKUP(A1,Sheet2!A1:B3,2)</TD></TR></TBODY></TABLE></TD></TR></TBODY></TABLE>
Excel 2003<TABLE style="BORDER-RIGHT: #a6aab6 1px solid; BORDER-TOP: #a6aab6 1px solid; BORDER-LEFT: #a6aab6 1px solid; BORDER-BOTTOM: #a6aab6 1px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff" cellPadding=2 rules=all><COLGROUP><COL style="BACKGROUND-COLOR: #e0e0f0" width=25><COL><COL></COLGROUP><THEAD><TR style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0; TEXT-ALIGN: center"><TH></TH><TH>A</TH><TH>B</TH></TR></THEAD><TBODY><TR><TD style="COLOR: #161120; TEXT-ALIGN: center">1</TD><TD style="TEXT-ALIGN: right">720</TD><TD style="TEXT-ALIGN: right">28</TD></TR><TR><TD style="COLOR: #161120; TEXT-ALIGN: center">2</TD><TD style="TEXT-ALIGN: right">740</TD><TD style="TEXT-ALIGN: right">30</TD></TR><TR><TD style="COLOR: #161120; TEXT-ALIGN: center">3</TD><TD style="TEXT-ALIGN: right">760</TD><TD style="TEXT-ALIGN: right">32</TD></TR></TBODY></TABLE><TABLE style="BORDER-RIGHT: #a6aab6 1px solid; BORDER-TOP: #a6aab6 1px solid; BORDER-LEFT: #a6aab6 1px solid; BORDER-BOTTOM: #a6aab6 1px solid; BORDER-COLLAPSE: collapse; BACKGROUND-COLOR: #ffffff" cellPadding=2 rules=all><THEAD><TR style="COLOR: #161120; BACKGROUND-COLOR: #e0e0f0; TEXT-ALIGN: center"><TH>Sheet2</TH></TR></TD></THEAD><TBODY></TBODY></TABLE>
Note: In Sheet1, column A is 720, 740, 760... not "720 - 740", "740 - 760" etc...