主题：GroupTableBuilder函数对某分组单元格空值忽略不计如何解决?

Dim g As New GroupTableBuilder("清单1",DataTables("H_YIZ"))
g.Groups.AddDef("住院ID")
g.Groups.AddDef("类别")
g.Groups.AddDef("项目")
g.Groups.AddDef("规格")
g.Groups.AddDef("单位")
g.Groups.AddDef("单价")
g.Totals.AddDef("用量")
g.Totals.AddDef("天数")
g.Build()

With DataTables("清单1")
    .DataCols.Add("余额", GetType(Double), "[单价] * [用量] * [天数]")
End With

for i as integer = 0 to datatables("H_YIZ").DataRows.count-1
    if currenttable(i,"单位") = "^_^" then
        currenttable(i,"单位") = ""
    end if
next