Try this
Sub Txt2Col()
Dim rng As Range
Set rng = [C7]
Set rng = Range(rng, Cells(Rows.Count, rng.Column).End(xlUp))
rng.TextToColumns Destination:=rng, DataType:=xlDelimited, ' rest of your settings
Update: button click event to act on another sheet
Private Sub CommandButton1_Click()
Dim rng As Range
Dim sh As Worksheet
Set sh = Worksheets("Sheet2")
With sh
Set rng = .[C7]
Set rng = .Range(rng, .Cells(.Rows.Count, rng.Column).End(xlUp))
rng.TextToColumns Destination:=rng, DataType:=xlDelimited, _
TextQualifier:=xlDoubleQuote, _
ConsecutiveDelimiter:=False, _
Tab:=False, _
Semicolon:=False, _
Comma:=True,
Space:=False,
Other:=False, _
FieldInfo:=Array(Array(1, xlGeneralFormat), Array(2, xlGeneralFormat), Array(3, xlGeneralFormat)), _
TrailingMinusNumbers:=True
End With
End Sub
Note the .'s (eg .Range) they refer to the With statement object