Error trying to loop through merged cells in a range?

Sub Try_This_For_Now()
Dim lr As Long, i As Long
Dim ma1 As Long, ma2 As Long
ma1 = Cells(3, 1).MergeArea.Columns.Count
ma2 = Cells(3, 17).Columns.Count
lr = Cells(Rows.Count, 1).End(xlUp).Row
    For i = 3 To lr Step Cells(3, 1).MergeArea.Rows.Count
        With Cells(i, 1)
            If .Value <> "" And .Offset(, 17 - ma1).Value <> "" Or .Value <> "" And .Offset(, 26 - ma1 - ma2 + 1).Value <> "" Then
                MsgBox "Data missing, try again!"
                    Else
                'Do here what needs to be done
            End If
        End With
    Next i
End Sub

Re: "I cannot unmerge the cells due to the nature of the form"
A re-design of the form is required. Might take some time but eliminates future problems.
Do a web search on why not to use "Merge & Center" in Excel. You'll be surprised at how many hits you'll get.