Help please, VBA userform, MsgBox!

Hello.

I have a userform that I use to introduce some data on excel.

Most of the data must be filled (that are textbox that the verifications dont need the information to do the calculations), because if they are not filled the rest of the worksheet cant do the verifications that I need.

When I click on the button "insert data",the textboxs that are mark with the red spot must be filled, if one of those textboxs aren't filled a msg box appears and says "Some data are missing, so the data can't be introduce on the worksheet".

So, I need to program the button insert, to only insert if the labels with the red spot are filled, and if they aren't filled to show me a msgbox.

Please, please, can anyone help me?

Thanks!