You may use InStr() or Split() to get the two parts of an assignment.

Using InStr():
code:
$sLine="value=123"
$iEqualIndex=InStr($sLine,"=")
If $iEqualIndex
   $sParameter=SubStr($sLine,1,$iEqualIndex-1)
   $sValue=SubStr($sLine,$iEqualIndex+1,9999)
EndIf
"Parameter '" $sParameter "' is assigned value '" $sValue "'" ?
Using Split():
code:
$sLine="value=123"
$asAssignment=Split($sLine,"=")
If UBound($asAssignment)
   "Parameter '" $asAssignment[0] "' is assigned value '" $asAssignment[1] "'" ?
EndIf
One reason you may be getting multiple lines is that Open() will not truncate an existing file. Each time you run the script the output will be appended to existing data. If you run the script three times you will get the line three times in the file.

Consider deleting the output file before you start.