Delete Unrecognized Character In Text File

I am trying to read a text file into a variable with VBA. The files I try to read usually have a bunch of unrecognized characters in them and I can't seem to read through them. I am looking for some code that will delete all unrecognized characters until it finds a string I specify.

Example of file

ΚW   

¾J Y

D Y
³F Y
ZE Y
¨B Z
˜6 Z

GOOD DATA

My code works fine if I manually delete all this stuff before GOOD DATA, but wont work if I dont. My "responseposition" is always 0 unless I delete all the nonsense.

Sub findvalues()

Dim strText As String

strText = GetFileContent("C:currentday.gdbm")

cardstring = "GOOD DATA"
responsePosition = InStr(1, strText, cardstring, vbTextCompare)

MsgBox (responsePosition)

End Sub