CASE: This way (3) NULLs get put in tbl if data is blank.

command = New SqlCommand("INSERT INTO tblFoo (UIAcctNum, WorkZip, CheckRouteDesc, Agency, Division, RUN, Rpt_Unit_RUNDesc, StartDate,EndDate ,CheckRouteCode, Rpt_Unit_RUNDesc__old,NAICS) " & _ 
" VALUES (@UIAcctNum, @WorkZip, @CheckRouteDesc, @Agency, @Division, @RUN, " & _ 
"CASE WHEN ltrim(@Rpt_Unit_RUNDesc) = '' THEN NULL ELSE @Rpt_Unit_RUNDesc END, " & _ 
"@StartDate, " & _ 
"CASE WHEN ltrim(@EndDate) = '' THEN NULL ELSE @EndDate END, " & _ 
"@CheckRouteCode, " & _ 
"CASE WHEN ltrim(@Rpt_Unit_RUNDesc__old) = '' THEN NULL ELSE @Rpt_Unit_RUNDesc__old END, " & _ 
" CASE WHEN ltrim(@NAICS) = '' THEN NULL ELSE @NAICS END)", connection) ' This way (3) NULLs get put in tbl if data is blank.