Just surround your value with quotation marks. Maybe you need to define quotation marks as "text quoting character" - not sure about right translation, have only german Excel here. Excel then imports this value into one cell. Look at this example:

spalte1    spalte2
wert11    wert12
wer21    "wer
t22"
[download]

this will result in a 2*3 excel sheet with B3 containing a string "wer<newline>t22".

tested with MS Excel 2007