Looping Through Files In Multiple Folders Searching For Certain Values

I'm trying to code a macro to search through all the files in certain folders to find a value defined by the user. The rows containing that value will then be copied and pasted into a separate workbook. My boss currently planning on storing about 550 different files (90 days worth of data) between these folders, but there is the possibility of years worth of data collection, should he change his mind about the 90 days, so I'd like the code to be efficient if possible. What I've tried to do is search each file for the value, then set a range equal the first row containing that value. If the value is found in that workbook, the code loops through the worksheet, adding all the other rows with that value to the range. Then the file looping exits (the values I'm looking for are only contained in one of the workbooks) and the range is copied and pasted into the master workbook. Each workbook has only one sheet.

I'm currently getting a run-time error "13" Type Mismatch error when it gets to the line where the code is supposed to find the value and initialize the range.

Code:
Private Sub SubmitButton_Click()

Dim mybook As Workbook
Dim masterbook As Workbook
Dim rownunm As Long
Dim pathparts(1 To 5) As String

[Code] ......