Error in filter

[mtrsoft]

I am working on an aplication that has a filter.
there is a combobox to choose the filter options. and a button is clicked to show the data. the filter only works the first time you choose the option. but after that when you want to choose another option you get a error message.

enclosed is the error message that we are recieving, and a copy of the code for the click event of that button.