Vba code for userform to search by range of date

Hi guys

Before my question i just want to say that this forum and the people here are amazing ;-)

Ok, now to the point...Can anyone give me a hand with a code to this sample file?
I have one file of this every month. In this sample i just have 2 materials, and this controls the stocks. I have design a userform with what i want (if its possible), and it consists in a combobox where i can select the material (in this sample there are LA-48, and Sact, but there are plenty more...maybe 20 but i hope that with your help with a code i can just add the others). Then i have two calendars where i introduce the start date and in the other the end date to use as a range to give me the sum of the inīs or the outīs, if i press one or another of this buttons (In / Out).
The result should appear in the textbox below and in the last textbox should appear the actual stock at the end date selected on the calendar (End). If its blank, or 0,or negative it should appear that way in the textbox.
Thanks in advance

Sample file.xls