4 digit Keypad Number entry converted to a Word variable?

I am controlling a door latch with a 16F870 and MOSFET. (I am fully documenting this and will look to post when all together)
I currently have a static variable LatchTime hardcoded.
I am in the process of converting this code to allow the LatchTime to be a user variable entered via the keypad. I have thought about the process and wanted to see if anybody had come up with a simple and efficient process or is this the way?

Example code to illustrate the theory (Not tested: as at work - Lunch Hour)

Dim Key1 as Word
Dim Key2 as Word
Dim Key3 as Byte
Dim Key4 as Byte

Dim LatchTime as Word

Key1 = Key1 * 1000
Key2 = Key2 * 100
Key3 = Key3 * 10
Key4 = Key4 * 1 ' Not required, but for illustration

LatchTime = Key1 + Key2 + Key3 + Key4

Latch High
DelayMS LatchTime
Latch Low

and also record this in the internal E2Prom.