Here's a routine I use to figure the number of lines it will take to print plain text, given a width. It works for me, but your mileage may vary.
Function getNumLines(prn As PrintPreview5.Preview, ByVal printText As String, ByVal fitWidth As Variant) As Integer
'This routine will determine how many lines a plain text string will take to print given a width
'prn is the previously defined preview control
'printText is the text string to be printed
'fitWidth is the width that you want to print the text in
'getNumLines returns the number of lines (integer)
'Dimension a few variables.
'i is a counter
'splitText() is an array that will be filled with each word (space delimited)
'tmpText is a junk variable
Dim i As Integer
Dim splitText() As String
Dim tmpText As String
'See how many lines it is, given the width
'Begin with one line
getNumLines = 1
'Split the text into the splitText array (space delimited)
splitText = Split(printText, " ")
'Initialize our temp string
tmpText = ""
'Loop through the array of words, adding one at a time to the tmpText variable
'Each loop, check the text width. If it is still less than the fitWidth, then keep adding words.
'If the text width is greater than the fit width, remove the last word added, add a line to getNumLines,
'and clear the tmpText variable. Keep going until all the words have been added.
For i = LBound(splitText) To UBound(splitText)
tmpText = Trim(tmpText & " " & splitText(i))
If prn.TextWidth(tmpText) > prn.C_Twips(fitWidth) Then
getNumLines = getNumLines + 1
tmpText = splitText(i)
'Now, in case the string is only one word, make sure it only returns one line
If Trim(splitText(0)) = Trim(printText) Then
getNumLines = 1