PSH> $ovo=new-object -com ovoautomation.opcmsg
PSH> $ovo|gm




TypeName: System.__ComObject#{bb03cab1-2606-4388-bbbc-2b5af2321464}

Name MemberType Definition
---- ---------- ----------
Send Method void Send ()
Application Property {get} {set}
MessageGroup Property {get} {set}
MessageId Property string MessageId () {get}
MessageText Property {get} {set}
NodeName Property {get} {set}
Object Property {get} {set}
OptVar Property {get} {set}
ServiceName Property {get} {set}
Severity Property {get} {set}

You'll note that 'Definition' section doesn't look very complete if compared
to the IE COM object.

What's gets me from here is that I cannot do something like:
PSH> $ovo.messagetext="testing"
Exception setting "MessageText": "Type mismatch. (Exception from HRESULT:
0x80020005 (DISP_E_TYPEMISMATCH))"
At line:1 char:6
+ $ovo.m <<<< essagetext="testing"
PSH>