Remove column which has expression set

Question

I want to remove a column from datatable 

the column is a part of expression I want to remove it once the expression is calculated.

Lower.Expression = "(Convert(µ,'System.Double')-Convert(LSL,'System.Double'))/(3.0*sigma)";
Upper.Expression = "(Convert(USL,'System.Double')-Convert(µ,'System.Double'))/(3.0*sigma)";
CpK.Expression = "IIF(Lower < Upper, Lower, Upper)";


I want to remove lower and upper once the data is populated