Runtime 91 in search pattern in Excel VBA (and in your code) is error if nothing is found. Use
On error resume next 'Enable error handler
Selection.Find ... 'Your find command with corrected parenthesis
On Error goto 0 'Disable Error handler
You have no problem. Except this errors down. Parenthesis closes on wrong location. (I assume that this is only error when you put code here as Excel will make error pop up for this also )
mailmwo.Selection.Find(What:=mwonum[B])[/B], After:=ActiveCell, LookIn:=xlFormulas _
, LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, _ ' <- line generated by Excel macro record
It should close before .Activate on find like this
mailmwo.Selection.Find(What:=mwonum, After:=ActiveCell, LookIn:=xlFormulas _
, LookAt:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:= _
False, SearchFormat:=False[B])[/B].Activate
red lines are lines that I had to add to get to .Activate