i have one idea to solve the problem but unable to program it in vba
hope sumbody wud help me out

the idea is

say we have values in column A & column B

for each r in my range
(columnA) [columnB]

if r.activecell.value <"" and r.offset(0,1).value = "" then

call Sub FillColBlanks

else

move to next row and make it as active cell

Sub FillColBlanks()
'by Dave Peterson 2004-01-06
'fill blank cells in column with value above
Dim wks As Worksheet
Dim rng As Range
Dim LastRow As Long
Dim col As Long

Set wks = ActiveSheet
With wks
col = ActiveCell.Column
'or
'col = .range("b1").column

Set rng = .UsedRange 'try to reset the lastcell
LastRow = .Cells.SpecialCells(xlCellTypeLastCell).Row
Set rng = Nothing
On Error Resume Next
Set rng = .Range(.Cells(2, col), .Cells(LastRow, col)) _
.Cells.SpecialCells(xlCellTypeBlanks)
On Error GoTo 0

If rng Is Nothing Then
MsgBox "No blanks found"
Exit Sub
Else
rng.FormulaR1C1 = "=R[-1]C"
End If

'replace formulas with values
With .Cells(1, col).EntireColumn
.Value = .Value
End With

End With

End Sub