在VB.Net中，可以使用以下代码来按条件拆分工作表：

1. 首先，创建一个工作簿对象，并打开要拆分的工作表：

Dim excelApp As New Excel.Application
Dim workbook As Excel.Workbook = excelApp.Workbooks.Open("路径\文件名.xlsx")
Dim worksheet As Excel.Worksheet = workbook.Worksheets("工作表名")

2. 然后，定义一个用于拆分工作表的条件，例如按照某一列的数值进行拆分：

Dim conditionColumn As Integer = 1 '条件所在的列号
Dim lastRow As Long = worksheet.Cells(worksheet.Rows.Count, conditionColumn).End(Excel.XlDirection.xlUp).Row '最后一行
Dim conditionValue As String '条件的值
Dim newWorksheet As Excel.Worksheet '新的工作表对象

For i As Integer = 2 To lastRow '从第2行开始，因为第1行通常是表头
    conditionValue = worksheet.Cells(i, conditionColumn).Value
    newWorksheet = workbook.Sheets.Add(After:=workbook.Sheets(workbook.Sheets.Count)) '在最后添加一个新的工作表
    newWorksheet.Name = conditionValue '以条件的值作为工作表的名称
    worksheet.Rows(i).Copy(newWorksheet.Rows(newWorksheet.Rows.Count)) '复制整行数据到新的工作表
Next

3. 最后，保存和关闭工作簿：

workbook.Save()
workbook.Close()
excelApp.Quit()

完整的示例代码如下：

Imports Excel = Microsoft.Office.Interop.Excel

Module Module1

    Sub Main()
        Dim excelApp As New Excel.Application
        Dim workbook As Excel.Workbook = excelApp.Workbooks.Open("路径\文件名.xlsx")
        Dim worksheet As Excel.Worksheet = workbook.Worksheets("工作表名")

        Dim conditionColumn As Integer = 1
        Dim lastRow As Long = worksheet.Cells(worksheet.Rows.Count, conditionColumn).End(Excel.XlDirection.xlUp).Row
        Dim conditionValue As String
        Dim newWorksheet As Excel.Worksheet

        For i As Integer = 2 To lastRow
            conditionValue = worksheet.Cells(i, conditionColumn).Value
            newWorksheet = workbook.Sheets.Add(After:=workbook.Sheets(workbook.Sheets.Count))
            newWorksheet.Name = conditionValue
            worksheet.Rows(i).Copy(newWorksheet.Rows(newWorksheet.Rows.Count))
        Next

        workbook.Save()
        workbook.Close()
        excelApp.Quit()
    End Sub

End Module

请注意，以上代码使用了Excel对象库，因此需要在项目中添加对"Microsoft Office 16.0 Object Library"的引用。另外，路径、文件名、工作表名可以根据实际情况进行修改。