Excel macro to add html tags to specific phrases in one worksheet

Sub format_html()
Dim alt_answer(5)
xRow = 4
Do Until xRow >= Range("A65536").End(xlUp).Row
tilde_text = Cells(xRow - 2, 1).Value
amper_text = Cells(xRow - 1, 1).Value
For x = 0 To 4
a = Split(Cells(xRow + x, 1).Value, ".")
search_val = Trim(a(1))
replace_val = "<font color = " & Chr(34) & "#008000" & Chr(34) & ">" & search_val & "</font>"
    tilde_text = Replace(tilde_text, search_val, replace_val)
    amper_text = Replace(amper_text, search_val, replace_val)
Next x
Cells(xRow - 2, 1).Value = tilde_text
Cells(xRow - 1, 1).Value = amper_text
xRow = xRow + 9
Loop
End Sub