Thanks for your help Matt....that worked. I passed the function to a variable after I got the number values then passed the values with the function to the html table:
#Format numerical data using the Get-FriendlyUnit Function before passsing string to HTML Table
$Cap = Get-FriendlyUnit -Value $Capacity | %{"{0,7:f2} {1,2}" -f $_.Value,$_.Unit}
$Prov = Get-FriendlyUnit -Value $Provisioned | %{"{0,7:f2} {1,2}" -f $_.Value,$_.Unit}
$Free = Get-FriendlyUnit -Value $FreeSpace | %{"{0,7:f2} {1,2}" -f $_.Value,$_.Unit}
$USpace = Get-FriendlyUnit -Value $Used | %{"{0,7:f2} {1,2}" -f $_.Value,$_.Unit}
$Cond1 = If ($Capacity -gt $Provisioned)
{"<td><font face='Tahoma'>$Prov</font></td>"}
ElseIf ($Capacity -lt $Provisioned)
{"<td><font face='Tahoma'color = 'red'>$Prov</font></td>"}
$Cond2 = if ( ($PercFree -lt $Warning) -and ($PercFree -gt $Critical) )
{"<td><font face='Tahoma'color = 'orange'>$PercFree</font></td></tr>"}
ElseIf ($PercFree -lt $Critical)
{"<td><font face='Tahoma'color = 'red'>$PercFree</font></td></tr>"}
Else
{"<td><font face='Tahoma'color 'black'>$PercFree</font></td></tr>"}
#Write output to html table
###########################
$tableEntry = "<td><font face='Tahoma'>$Name</font></td>" +
"<td><center><font face='Tahoma'>$Cap</font></center></td>" +
$Cond1 +
"<td><center><font face='Tahoma'>$Free</font></center></td>" +
"<td><center><font face='Tahoma'>$USpace</font></center></td>" +
$Cond2
Add-Content $fileName $tableEntry
Write-Host $tableEntry
}