There can be many ways to spot a ranging market. Here are a couple of them (#2 is one of favourite):

#1 (price is sitting within a specified range, within the most recent periods):

HH = highest[40](high]
LL = lowest[40](low)
IsRange = (HH - LL) <= 20 * PipSize

#2 (Bollinger Bands are both inside a Donchian Channel):

//------------------------------------------------------------------------------------
//                            BB - Bollinger Bands
BBval        = 20                                       //6     periodi BB
BBdev        = 2.00                                     //2.00  deviazione BB
BBAvgType    = 0                                        //0  =  sma
BBavg        = average[BBval,BBAvgType](close)          //BB    mean (middle line)
BollUP       = BBavg + ((std[BBval](close)) * BBdev)    //BB    Upper Band
BollDN       = BBavg - ((std[BBval](close)) * BBdev)    //BB    Lower Band
//------------------------------------------------------------------------------------
//                            Donchian Channel
//
DonchianP    = BBval
DonchianUP   = HIGHEST[DonchianP](HIGH[1])
DonchianDN   = LOWEST[DonchianP](LOW[1])
//------------------------------------------------------------------------------------
IsRange      = (BollUP <= DonchianUP) AND (BollDN >= DonchianDN)

Use the variable IsRange to take any action.