Presumably you want something like:
Code:
Filename = TBM1Customer.Text
If Dir(strFldrPath & Filename) <> "" Then
Workbooks.Open Filename:=strCustFile
Else
MsgBox Title:="File Not Found", _
Prompt:="File """ & Filename & """ not found in " & strFldrPath
End If
PS: When posting code, please use the code tags, indicated by the # button on the posting menu. Without them, your code loses much of whatever structure it had.