一旦工作簿中的Excel表保存为.csv，就无法回到.xlsm

I have a workbook with multiple sheets. I press a (ribbon) button and a subroutine saves multiple sheets as .csv, shells out to some java code, then comes back. The problem is: once it comes back, the workbook has been converted to a .csv file (the last one saved) and no further .xlsm operations are possible. I have a workbook with multiple sheets. I press