Increase digits after decimal to 4

Hi all,

Below snapshot is of AP>Invoice Journal>Lines>Withholding tax.. I want 'withhold tax amount ' to be calculated till 4 decimals.In setup parameter i have increased the decimal to 4 for the field which is used to calculate the value.When i debug on this form value of amount comes from TmpTaxWithholdWorkTrans_IN.SourceTaxAmountCur... I am not able to find where can i change this 2 decimals to 4 decimals.

Please kindly look in issue and try to help.

Thanks in advance.