XlLookAt
type XlLookAt = xlWhole | xlPartDescription
Specifies whether the whole search text or any part of the search text is matched.
Try It
var oSearchRange = oRange.Find( { What: "200", After: oWorksheet.GetRange("B1"), LookIn: "xlValues", LookAt: "xlWhole", SearchOrder: "xlByColumns", SearchDirection: "xlNext", MatchCase: true } );