CM SNMP question

Yes There is

docsIfCmtsCmStatusUpChannelIfIndex (1.3.6.1.2.1.10.127.1.3.3.1.5)

it is indexed by docsIfCmtsCmStatusIndex which I call a modemId

you can get the modemid by querying the following docsIfCmtsCmStatusMacAddress this grabs the modemId by mac address the mac address is encoded as decimal by each octet.
here is some PHP code to get the modemId
<?php
function getModemId($macAddress, $cmtsAddress, $community) {
$formattedMac = split("_", ereg_replace("_$", "", chunk_split($macAddress, 2, "_")));
$formattedMac2 = array_map("hexdec", $formattedMac);
$formattedMac = join (".", $formattedMac2);
snmp_set_quick_print(1);
$modemId = snmpget($cmtsAddress, $community, ".1.3.6.1.2.1.10.127.1.3.7.1.2." . $formattedMac);
return $modemId;
}
function getUpstreamInterface($modemId, $cmtsAddress, $community) {
snmp_set_quick_print(1);
//Get Upstream Index
$upstreamIndex = snmpget($cmtsAddress, $community, "1.3.6.1.2.1.10.127.1.3.3.1.5." . $modemId);
$upstreamName = snmpget($cmtsAddress, $community, "1.3.6.1.2.1.2.2.1.2.".$upstreamIndex);
return $upstreamName;
}

//Given the mac 000011112222 you would do this
$modemId = getModemId("000011112222", "10.0.0.1", "public");
$upstreamName = getUpstreamInterface($modemId, "10.0.0.1", "public");
?>