Simple way:
 Code:
$Tmp = Val($NumberString)
If $Tmp <> $NumberString
  'ERROR - ' $NumberString ' contains non-numeric chars!' ?
EndIf
It's quick and dirty, but won't handle numbers containing commas, which might be legal. A better way would be to enumerate the string, comparing each char against a list of allowed chars - basic data validation:
 Code:
$Allowed = '0123456789.,'
For $P = 1 to Len($NumString)
  $C = SubStr($NumString, $P, 1
  If Not InStr($Allowed, $C)
    $C ' is an invalid char - aborting!' ?
    Exit 1
  EndIf
Next
This same logic can be used to validate any type of data.

Glenn
_________________________
Actually I am a Rocket Scientist! \:D