Have you configured IP locations.
Because if you have done this you can filter on the name of the ip location instead of the start and end ip.
You can then use the following report that filters on a specific ip location. Please change the red word with the name of the ip location that you want to filter on.
Select Top 1000000 tblAssets.Domain,
tblAssets.AssetName,
tblOperatingsystem.Caption,
tblAssets.Lastseen,
tsysIPLocations.StartIP,
tsysIPLocations.EndIP,
tblAssets.IPNumeric,
Round((Cast((DateDiff(mm, tblBIOS.ReleaseDate, GetDate())) As float) / 12),
0) As [PC Age]
From tblAssets
Inner Join tblAssetCustom On tblAssets.AssetID = tblAssetCustom.AssetID
Inner Join tsysAssetTypes On tsysAssetTypes.AssetType = tblAssets.Assettype
Inner Join tblOperatingsystem
On tblAssets.AssetID = tblOperatingsystem.AssetID
Inner Join tblBIOS On tblAssets.AssetID = tblBIOS.AssetID
Inner Join tsysIPLocations On tblAssets.IPNumeric >= tsysIPLocations.StartIP
And tblAssets.IPNumeric <= tsysIPLocations.EndIP
Where tblOperatingsystem.Caption = 'Microsoft Windows 7 Professionnel'
And tblAssetCustom.State = 1 And tsysIPLocations.IPLocation =
'
name ip location'