You didn't specify wether you wanted the output formatted in anyway, so here's a really simple method:
Code:
Private Sub Command1_Click()
Dim iFile As Integer
Dim iCell As Long
iFile = FreeFile
Open "C:\Grid.txt" For Output As iFile
With MSFlexGrid1
For iCell = 0 To (.Cols * .Rows) - 1
Print #iFile, .TextArray(iCell)
Next
End With
Close iFile
End Sub