Do you mean you want an inputbox to appear that allows you to enter the string that it will search
for, and then delete those rows. If so then try the following tweak of Chip's code:-
Sub DelRowsIf()
Dim RowNdx As Long
Dim LastRow As Long
Dim ans As String
ans = InputBox("What string do you want rows to be deleted if it contains it?")
LastRow = ActiveSheet.Cells(Rows.Count, "A").End(xlUp).Row
For RowNdx = LastRow To 1 Step -1
If StrComp(Cells(RowNdx, "A"), ans, vbBinaryCompare) = 0 Then
Cells(RowNdx, "A").EntireRow.Delete
End If
Next RowNdx
End Sub