Data validation macro - excel

Question

I'm creating an Excel sheet which different people are going to add to, so am wondering if there's any simple way to check for the row where user starts writing being filled?
For example, if user starts typing in cell A1, macro checks if the cells are filled on the same row.
Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
Dim rsave As Range
Dim cell As Range
Set rsave = Sheet1.Range("a1:i1")
For Each cell In rsave
If cell = "" Then
Dim missdata
missdata = MsgBox("missing data", vbOKOnly, "Missing Data")
Cancel = True
cell.Select
Exit For
End If
Next cell
End Sub

Answer 1

to expand on the suggested solution, you can do the following. Instead of looping through each cell, your problem can be solved efficiently with two lines of code:
'get the used range
Set rsave = Sheet1.Range("a1:i1")
'Select all blank(not yet filled) cells
rsave.SpecialCells(xlCellTypeBlanks).Select
This will select all cells which've not been filled in the range a1:i1 of the sheet. Alternatively, you can use some colour to make it more explicit. If it works, don't forget to accept the answer.

Answer 2

If by saying "data validation", you mean check for blanks, you can use this:
Sub Test()
Dim wrng As Range
Set wrng = ActiveSheet.UsedRange
MsgBox "The data in a range: '" & wrng.Address & "' are" & IIf(IsValidData(wrng), "", "n't") & " valid"
Set wrng = Nothing
End Sub
Function IsValidData(rng As Range) As Boolean
IsValidData = rng.SpecialCells(xlCellTypeBlanks).Count = 0
End Function
Note, that the UsedRange method returns a range starting from A1 cell. So, you need to add extra code to select a range occupied by the data (skip blanks rows and columns).
Sub Test()
Dim wrng As Range
Set wrng = GetDataRange()
MsgBox "The data in a range: '" & wrng.Address & "' are" & IIf(IsValidData(wrng), "", "n't") & " valid"
End Sub
Function GetDataRange() As Range
Dim wrng As Range, c As Range, saddr As String
Dim pos As Integer
'get used range
Set wrng = ActiveSheet.UsedRange
'find first non-empty cell in a used range
saddr = ActiveSheet.Range(wrng.End(xlToLeft).Address, wrng.End(xlUp).Address).Address
pos = InStr(1, saddr, ":")
'skip blanks rows and set new range
Set GetDataRange = ActiveSheet.Range(Mid(saddr, pos + 1, Len(saddr) - pos) & ":" & wrng.SpecialCells(xlCellTypeLastCell).Address)
Set wrng = Nothing
End Function
Good luck!