Soul

Whatever you do don't add On Error Resume Next, unless you just want to hide the problem that is.

You also shouldn't have Set - MatB is not an object.

Actually that brings up something else, declare MatB as Variant not Long.

Also replace WorksheetFunction.Match with Application.Match.

You should do both of those things for ColA, ColB and ColC.

The reason MatB is 0 in the Immediate Window is because that's it's default value.

The reason Match fails is because there is no match - only one worksheet in the workbook has data, and it's not even that sheet that's active when the code runs.

Which worksheet should Columns("B:B") refer to?