Using A Form To Insert Values Into Separate WS

I am wanting to use a command button to bring up form {i have made the form and button for this]. Once it comes up, the user types in a date for which data point he will insert the usage. By pressing the execute button the user should be able to insert this value into the appropriate worksheet point. IN the end version on the form i will have multiple types of widgets. all that should happen is what the user inserts into the form will be inserted and replace the usage column value (i.e. column J of widget 1.45 WS). if the user leaves the box blank then nothing should happen to the relevent cell.